Speaker 1: Welcome back to the deep dive. Today, we're really getting
Speaker 1: our hands dirty, jumping into the practical world of Cisco
Speaker 1: CCNA commands.
Speaker 2: Yeah, exactly.
Speaker 1: Imagine you're setting up a network from scratch, maybe for
Speaker 1: a new office, a growing startup. Where do you even begin?
Speaker 2: Right?
Speaker 1: Our mission for you today is basically to pull out
Speaker 1: the absolute must know bits, give you a kind of shortcut,
Speaker 1: you know, so you feel ready to connect some dots.
Speaker 2: And what's really valuable here, I think, is that this
Speaker 2: guide we're looking at focuses on the commands you actually need. Beginner,
Speaker 2: intermediate level CCNA stuff, practical stuff exactly, stuff you can
Speaker 2: use on real gear or in the simulation labs for
Speaker 2: the exam. It's all about application.
Speaker 1: Okay, So first things first, before any configuration, you got
Speaker 1: to connect things right.
Speaker 2: Cabling the physical layer yep.
Speaker 1: Sounds basic maybe, but here's where it gets interesting, Like
Speaker 1: choosing the wrong cable that can completely sink your network
Speaker 1: before you type a single command.
Speaker 2: Oh absolutely, I've seen it happen. Hours wasted me too.
Speaker 1: I remember, spending age is troubleshooting once only to find YEP,
Speaker 1: crossover cable where a straight through should have been. Total
Speaker 1: face palm moment happens to the best of us. So
Speaker 1: the guide really stresses mastering this. Know you're streight through
Speaker 1: your crossover, your rollover cables.
Speaker 2: And the pinouts are key. It's the wiring inside, which
Speaker 2: pin connects to which get that wrong? No data flow,
Speaker 2: simple as that.
Speaker 1: And once it's plugged in, you need to check the
Speaker 1: config on the actual computers.
Speaker 2: Right, yeah, on the end devices, So like if you
Speaker 2: can FIG on Linux or Mac.
Speaker 1: Or IP can fig if you're on Windows, Windows two
Speaker 1: thousand and up.
Speaker 2: Basically, and this whole cabling thing, getting it right, it
Speaker 2: really sets the stage, doesn't it. Make sure you're not
Speaker 2: chasing hardware ghosts when the problem is actually software exactly.
Speaker 1: You don't want to be troubleshooting routing protocols. If the
Speaker 1: cable's just.
Speaker 2: Wrong, you're trying to drive a car with no wheels.
Speaker 1: Essentially, good analogy. Okay, so physically connected, now they need addresses.
Speaker 1: They need to speak the language of IP. Right, let's
Speaker 1: talk IP subnetting. Sounds a bit scary, maybe you can
Speaker 1: see in that way, but we'll break it down. Think
Speaker 1: about those IP address classes ABC.
Speaker 2: Mainly, Yeah, they're like different sizes of networks right.
Speaker 1: So Class A starts with a zero first number is
Speaker 1: zero to one twenty seven. That's your massive network like
Speaker 1: an ocean liner holds millions of devices.
Speaker 2: Huge organizations ISPs.
Speaker 1: Maybe Class B starts one zero numbers one twenty eight
Speaker 1: to one ninety one. That's maybe more like a large
Speaker 1: cargo ship medium to large businesses makes sense. And Class
Speaker 1: C starts one one zero numbers one ninety two to
Speaker 1: two twenty three. That's your small fishing boat home networks
Speaker 1: small offices holds a couple hundred addresses.
Speaker 2: Perfect for most smaller setups.
Speaker 1: Then you have Class D for multicasting like video streams
Speaker 1: to many people at once.
Speaker 2: Two hundred and twenty four to two thirty nine range.
Speaker 1: And Class E, which is reserved experimental stuff two forty.
Speaker 2: In up right, And the guide shows how computer see
Speaker 2: these numbers converting decimal to binary.
Speaker 1: Yeah, like one ninety two becomes one hundred and one
Speaker 1: hundred thousand, or two twenty four is eleven hundred and
Speaker 1: fetter thousand.
Speaker 2: So that familiar private IP one ninety two point one
Speaker 2: sixty eight point two five four point twenty five four
Speaker 2: The router sees it as a one one hundred zero
Speaker 2: zero zero zero one zero one one zero zero point
Speaker 2: one one one on a narrow point one one one
Speaker 2: one one one point one one one one one one
Speaker 2: one one binary.
Speaker 1: Okay, So how does the router use that?
Speaker 2: That's where binary ending comes in. It sounds technical, but
Speaker 2: it's fundamental. It's how devices figure out the network part
Speaker 2: of an address versus the host part.
Speaker 1: Like separating the street name from the house number exactly.
Speaker 2: It uses the IP address and the subnet mask. Think
Speaker 2: of it like a filter. Only where both the IP
Speaker 2: and the mask have a one bit, does a one
Speaker 2: come through in the result.
Speaker 1: Okay?
Speaker 2: The logic is simple zero no zero one and no
Speaker 2: zero zero one is a one bit only one on
Speaker 2: one gives you one, got it? So take that one
Speaker 2: ninety two point one sixty eight point two five four
Speaker 2: point two five four Again. If your mask is two
Speaker 2: five five point two five five point zero point zero,
Speaker 2: which is all ones in the first two oct it's
Speaker 2: when you endy them together binary style. Get one ninety
Speaker 2: two point one sixty eight point zero zero. That's the
Speaker 2: network number. That's how your device knows if another IP
Speaker 2: is on the same local network or somewhere else. Right.
Speaker 1: Okay, that makes sense. So wired up addresses understood. Now,
Speaker 1: how do we talk to these Cisco devices, routers, switches.
Speaker 2: That's the command line interface, the CLI, your.
Speaker 1: Direct line in no fancy graphics, just task commands.
Speaker 2: Pretty much. It's the primary way you can figure and
Speaker 2: manage Cisco gear.
Speaker 1: And there are shortcuts right right to save.
Speaker 2: Typing Oh yeah, tons of them, big time savers like
Speaker 2: typing COF then hitting the TB key It autocompletes to
Speaker 2: configure terminal nice or just for able to get into
Speaker 2: privilege mode.
Speaker 1: Very handy, but you still need to know the full
Speaker 1: command for exams usually.
Speaker 2: Definitely good point. The shortcuts are for efficiency on the job.
Speaker 1: And what if you forget a command or aren't sure
Speaker 1: what options are available?
Speaker 2: The question mark your best friend on the CLI? Yeah yep.
Speaker 2: Just type bought on its own shows you all commands
Speaker 2: in that mode. Type C or N shows commands starting
Speaker 2: C or N or type of command like clock, then
Speaker 2: a space then and it shows you what words or
Speaker 2: parameters can come next. Super helpful, like a built in.
Speaker 1: What about the setup mode? The guide mentions is that useful?
Speaker 2: Not really for most people. It kicks in automatically if
Speaker 2: a device has zero configuration.
Speaker 1: Like brand new out of the box exactly, or you.
Speaker 2: Can type set up. It's like a basic wizard, ask
Speaker 2: you questions, but it's very limited.
Speaker 1: Can't do much with it.
Speaker 2: Nope, basic IP stuff maybe a password, no ACLS, no NAT.
Speaker 2: Serious configuration requires the CLI. Most engineers skip.
Speaker 1: It, gotcha, stick to the CLI definitely.
Speaker 2: And speaking of the CLI, there are even more shortcuts,
Speaker 2: like keyboard shortcuts that really boost productivity. Oh like what well,
Speaker 2: Ctrl plus z is amazing, jumpt you right back to
Speaker 2: privileged mode from anywhere, and configu mode saves typing end
Speaker 2: or exit multiple times. Oh I like that. Ctrl plus
Speaker 2: F moves forward a character, ec plus b moves back
Speaker 2: a whole word. Ctrl plus e takes you to the
Speaker 2: end of the line you're typing.
Speaker 1: Handy for fixing typos totally.
Speaker 2: And then there's command history. Ctrl plus P recalls previous
Speaker 2: commands ctr we'll plug and recalls newer ones if you
Speaker 2: went back too.
Speaker 1: Far, so you don't have to retype everything exactly.
Speaker 2: And you can even control how many commands get remembered
Speaker 2: with terminal history size. And then a number. Default is
Speaker 2: often just ten, but you can bump it up maybe
Speaker 2: to fifty or one hundred max is two fifty six?
Speaker 1: Why not? I always set it to max.
Speaker 2: It uses a bit of router memory, probably not noticeable
Speaker 2: on modern gear, but something to be aware of. There's
Speaker 2: always a trade off. You can reset it with no
Speaker 2: terminal history size. Okay. Cool.
Speaker 1: Now, once you're configuring things, you need to see what's
Speaker 1: going on right.
Speaker 2: Verify stuff absolutely. That's where the show commands come in.
Speaker 2: They are indispensable your eyes and ears inside the device.
Speaker 1: So if something's broken, where do you start? What are
Speaker 1: the key show commands?
Speaker 2: Great question, It's less about memorizing a list and more
Speaker 2: about thinking what do I need to check? I tend
Speaker 2: to group them. Okay. First, basic connectivity and interfaces. Show
Speaker 2: interfaces status gives you a quick look at all ports
Speaker 2: of they up, down, connected, show interface fast Internet oh
Speaker 2: one or whatever. It gives you detailed staff for that
Speaker 2: specific port, error speed.
Speaker 1: Duplex all right, checking the physical connection.
Speaker 2: Then ipaddressing DOT show interface brief is fantastic, quick summary
Speaker 2: dot interface, IP address is that up status protocol dot
Speaker 2: super useful, And show ARP shows the mapping between IP
Speaker 2: addresses and MC addresses the device has learned. Crucial for
Speaker 2: Layer two troubleshooting makes sense.
Speaker 1: What about the actual configuration.
Speaker 2: That's where show running config comes in. Shows you the
Speaker 2: active configuration what the device is using right now from
Speaker 2: ramp absolutely vibe and you compare that to show startup
Speaker 2: canfig that's the config saved and NVRMP the one the
Speaker 2: loads on boot. If they're different, you know you haven't
Speaker 2: saved your changes. Ah, the classic mistake happens all the time.
Speaker 2: Then for routing, show ip rout that's your routing table.
Speaker 2: How does this router know how to reach different networks?
Speaker 2: It's all in there. And show protocols tells you about
Speaker 2: the Layer three protocols.
Speaker 1: Configured, got it any others?
Speaker 2: Show version is good for checking the iOS software version, uptime,
Speaker 2: hardware info. Show history dumps your command history buffer. Show
Speaker 2: flash shows you the flash memory contents, Show clock for
Speaker 2: the time, Show hosts for any local host named it
Speaker 2: mappings you've set up.
Speaker 1: Wow. Okay, so show commands are really your window into
Speaker 1: the device.
Speaker 2: Absolutely you live and breathe Show commands when managing Cisco gear.
Speaker 1: Okay, let's zoom in on router. Specifically, they're the traffic
Speaker 1: cops directing packets between.
Speaker 2: Networks, directing the traffic.
Speaker 1: Yeah, and configuring them means understanding those different modes you
Speaker 1: mentioned earlier.
Speaker 2: Right, you start in user mode usually just router prelimited.
Speaker 2: Then enable gets you to privileged mode rater hashtag. Here
Speaker 2: you can run show commands, debugs, save can figs, but
Speaker 2: still can't make changes. For changes, you need configure terminal
Speaker 2: or can fig for short. That takes you into global
Speaker 2: configuration mode router can fig hashtag. This is where the
Speaker 2: real work happens, and from there you can go deeper. YEP,
Speaker 2: interface faster at a zero zero takes you to interface
Speaker 2: mode router configure hashtag or router ospe f one takes
Speaker 2: you to router configure mode reader figure outer hashtag. There
Speaker 2: are also modes for lines, can fig line the sub interfaces,
Speaker 2: config soubif key thing.
Speaker 1: Is different commands work in different modes.
Speaker 2: Exactly, And first thing you usually do in global config
Speaker 2: get the writer or a.
Speaker 1: Name post name R one or whatever post name name Yeah.
Speaker 2: Yeah. Good practice for identification.
Speaker 1: And security is paramount right passwords, oh absolute foundational.
Speaker 2: You've got two main enabled passwords.
Speaker 1: The ones to get into privileged mode.
Speaker 2: Right enable password password is the old way stores in
Speaker 2: plaintext and the config bad idea to so avoid that one, yes,
Speaker 2: always use enable secret password. This one uses stronger encryption
Speaker 2: MT five hashing usually much more secure, and if you
Speaker 2: can figure both the enabled secret wins, it always overrides
Speaker 2: the enabled password.
Speaker 1: Good to know. What about passwords for actually logging in,
Speaker 1: like over the console cable or remotely?
Speaker 2: Yep, you secure those lines too, Line console zero for
Speaker 2: the console port line VTIO four typically covers the five
Speaker 2: virtual terminal lines for Telnet or SSH, LINEO zero for
Speaker 2: the auxiliary report. In the commands inside the line config mode,
Speaker 2: use password to set it, and then critically you must
Speaker 2: type log in to tell a router to actually check
Speaker 2: for that password on login.
Speaker 1: Attempts okay password, then log in right.
Speaker 2: And there's also service password encryption. This command applies a
Speaker 2: very weak encryption to all plaintext passwords in the config
Speaker 2: like the line passwords or if you foolishly used enable password.
Speaker 1: Is it actually secure?
Speaker 2: Not really, it's easily breakable. It just stops casual shoulder surfing.
Speaker 2: Enable secret is the only strong one built in for
Speaker 2: the enabled password. If you turn off service password encryption later,
Speaker 2: any passwords that weakly encrypted stay that way.
Speaker 1: So just to be clear. Why is an able password
Speaker 1: such a bad idea? How quickly could that bite you?
Speaker 2: Instantly? If anyone gets a copy of your config file,
Speaker 2: maybe a backup, maybe through some other access, they just
Speaker 2: read the password. It's right there, no guessing, no cracking required,
Speaker 2: enable secret hashes it so even seeing the config doesn't
Speaker 2: give away the password directly. It's a basic essential secure step.
Speaker 1: Okay, message received, use an able secret. Now interfaces, the
Speaker 1: actual connections, how do we configure those?
Speaker 2: Right? So you navigate using interface followed by the type
Speaker 2: in number like interface cereal zero zero zero, interface faceter
Speaker 2: and at zero zero.
Speaker 1: And you warned the prompt doesn't always change.
Speaker 2: Yeah, it might just say rote or configu hashagg regardless
Speaker 2: of whether you're in serial zero zero, fascinated at zero zero,
Speaker 2: keep track, exit moves you back up one level.
Speaker 1: Okay. Let's say we're configuring a serial interface like for
Speaker 1: a WAN link.
Speaker 2: Okay, so interface serial zero zero zero zero. Good practice
Speaker 2: to add a description like description link to main office
Speaker 2: helps document things and the IP address, app dress, subnetmask,
Speaker 2: standard stuff.
Speaker 1: And the special thing for cereal the clock rate.
Speaker 2: If you have the DCE cable, the one providing the
Speaker 2: timing signal for the link You must set the clock
Speaker 2: rate speed command on that interface only needed on the
Speaker 2: DCE side.
Speaker 1: How do you know the speed?
Speaker 2: Usually determined by the service provider or the capabilities of
Speaker 2: the link fin no shutdown to actually turn the interface on,
Speaker 2: They're off by default? No shutdown? Got it?
Speaker 1: And for fast Ethernet like connecting to a land switch.
Speaker 2: Simpler interface fast Ethernet zero zero maybe a description then
Speaker 2: IP address, IP address, subnet mask and no shutdown. No
Speaker 2: clock rate needed there?
Speaker 1: Okay? What about those messages you sometimes see when you
Speaker 1: log into a device, like warnings or welcome messages.
Speaker 2: Ah banners? Yeah, you could set those banner mot hashtag,
Speaker 2: message here, hashtag attag. The hashtag is a deliminter. You
Speaker 2: can use any character not nut in your message. MOTD
Speaker 2: stands for Message of the day. When does that show
Speaker 2: up after successful log in? Usually there's also banner log
Speaker 2: in hashtag message hashtag which shows up before the login prompt.
Speaker 2: MOOTD usually takes precedence if both are set. Good for
Speaker 2: legal disclaimers or warnings?
Speaker 1: Cool? You mentioned show hosts earlier? Can you manually set those?
Speaker 2: You can use IPPO host name, IP address so you
Speaker 2: could do IIP post server one one nine two point
Speaker 2: one sixty eight point one one one on a zero.
Speaker 2: Then on that router you could potentially ping server one
Speaker 2: instead of the IP. It's just a local mapping on
Speaker 2: that device.
Speaker 1: Handy for remembering key servers.
Speaker 2: Yeah, and related to look ups. By default, if you
Speaker 2: type something the router doesn't recognize as a command, it
Speaker 2: tries to resolve it via DNS, thinking it's a host
Speaker 2: name you want to connect.
Speaker 1: To, and that can be slow. If you just made
Speaker 1: a typo.
Speaker 2: Exactly, it hangs for a bit. Try to contact a
Speaker 2: DNS server. You can turn that off with no IP
Speaker 2: domain lookup. Saves a lot of frustration from typos.
Speaker 1: Good tip. All right, any other really useful general commands
Speaker 1: we should know?
Speaker 2: Yeah, a few life savers. No logging synchronous ever. Typing
Speaker 2: a command and a console message like percent link fine
Speaker 2: you be down? Yeah, pops up right in the middle
Speaker 2: of your line.
Speaker 1: Yes, so annoying.
Speaker 2: No logging synchronous stops that. It ensures your command prompt
Speaker 2: reappears cleanly below the message, so you don't lose your place.
Speaker 1: Essential Okay, definitely using that one.
Speaker 2: Then exact timeout sets how long a console or vty
Speaker 2: session can be idle before it logs you out. Yeah,
Speaker 2: exact time out one hundred zero means ten minutes, zero seconds,
Speaker 2: good security practice. What about zero zero means never time out?
Speaker 2: Big security hole. Don't do that on production.
Speaker 1: Gear right, and saving your work crucial.
Speaker 2: Copy running config, startup config, or copyrun start for short
Speaker 2: saves the act of config from RAM to envy RAM.
Speaker 2: If you don't do this and the router reboots, all gone, yep, mistake,
Speaker 2: you only make ones. You can also erase startup config
Speaker 2: to wipe the save config for starting fresh and copy
Speaker 2: running config. TFTP lets you back up your config to
Speaker 2: a TFTP serve on the network. Good for disaster recovery.
Speaker 1: And that do command you mentioned right do.
Speaker 2: Let's say you're deep in interface configuration mode. Router can
Speaker 2: fig ashtag ETI. Normally to see the running config, you'd
Speaker 2: have to type end then show running config.
Speaker 1: Yeah, jump back out with do.
Speaker 2: You can just type do show running config right there
Speaker 2: in interface mode. It executes the show command without making
Speaker 2: you leave config mode. Huge time saver, but it doesn't
Speaker 2: work for everything. Doesn't work for commands that change your mode,
Speaker 2: like configure terminal itself, but for most show commands, ping
Speaker 2: trace for it.
Speaker 1: That's pert awesome, Okay configured. How do they learn about
Speaker 1: networks beyond the ones directly plugged into them?
Speaker 2: Ah, Now we get into routing. How riders build their
Speaker 2: maps of the internetwork.
Speaker 1: Starts with static routes the manual way.
Speaker 2: Often yeah, simple scenarios. The command is that brot, then
Speaker 2: the destination network, then the subnet mask of that destination,
Speaker 2: than how to get there. How to get there could
Speaker 2: be either the IP address of the next router in
Speaker 2: the path, next hopyup, or the router's own exit interface
Speaker 2: that leads toward that network. Example, it proved ten point
Speaker 2: one point two point zero two five five point two
Speaker 2: five five point two five five point zero one ninety
Speaker 2: two point one sixty eight point one point one that
Speaker 2: tells the router to reach the ten point one point
Speaker 2: two point zero network. Send packets to the router at
Speaker 2: one ninety two point one sixty eight point one point one.
Speaker 1: Simple enough, but they're temporary by default.
Speaker 2: Yeah. If the interface used to reach the next hop
Speaker 2: goes down, the static route disappears. From the routing table.
Speaker 2: You can add the permanent keyword at the end if
Speaker 2: you want it to stay even if the interface is down.
Speaker 2: But that's less common.
Speaker 1: Okay, But what if a router learn multiple ways to
Speaker 1: get to the same place, maybe a static route and
Speaker 1: also a dynamic protocol.
Speaker 2: Excellent question. That's where administrative distance or AD comes in.
Speaker 1: AD sounds important. It is.
Speaker 2: It's a number from zero to two fifty five that
Speaker 2: represents how trustworthy a routing source is. Lower number means
Speaker 2: more trustworthy, So the.
Speaker 1: Router picks the path with the lowest AD.
Speaker 2: Exactly if it learns about the same network from two
Speaker 2: different sources, it installs the route with the lower AD
Speaker 2: into the routing table.
Speaker 1: What are some typical AD values.
Speaker 2: A directly connected network has an AD of zero. Can't
Speaker 2: be that it's plugged right in, makes sense. A static
Speaker 2: route has a default AD of one, very trustworthy because
Speaker 2: you manually configured it. Okay, Then the dynamic protocols EIGRP
Speaker 2: is ninety, OSPF is one ten, RIP is one twenty.
Speaker 1: So EIGRP is preferred over OSPF, which is preferred over RIP.
Speaker 1: If they all offer a route.
Speaker 2: By default, yes, and two fifty five means totally untrusted,
Speaker 2: the route won't be used.
Speaker 1: Can you use this AD cleverly.
Speaker 2: Absolutely, that's the idea behind and floating static routes. Imagine
Speaker 2: you're running EI g RP eighty ninety as your main
Speaker 2: routing protocol. You could configure a static route for the
Speaker 2: same destination, but manually give it a higher AD, say
Speaker 2: one hundred.
Speaker 1: So normally the EIGRP route.
Speaker 2: Is used, right, but if the e I goop route disappears,
Speaker 2: maybe the link fails, the router sees the static route
Speaker 2: with eighty one hundred is now the best path, and
Speaker 2: it floats into the routing table as a backup.
Speaker 1: Ah cool, automatic backup.
Speaker 2: Exactly intelligent failover using AD. And then there are default
Speaker 2: routes the route of last resource decisely ap route one
Speaker 2: ozero point zero point zero point zero point zero point zero,
Speaker 2: followed by the next hop or exit interface. It basically means,
Speaker 2: if you don't have a specific route for this destination
Speaker 2: at your table, send it here, usually points towards your
Speaker 2: ISP or core network, and you check all this one
Speaker 2: shoe iproot your main command for viewing the routing table
Speaker 2: and seeing which routes are active. They're ad metric and
Speaker 2: how they were learned.
Speaker 1: Okay, so static routes are manual. What about the dynamic
Speaker 1: ones you mentioned RIP E I g r POSPF right.
Speaker 2: Those are the protocols routers used to automatically share routing
Speaker 2: information with each other, much more scalable for larger networks.
Speaker 1: Let's maybe touch on each one briefly, starting with RIP sure.
Speaker 2: RIP Routing Information Protocol. It's a pretty old simple distance
Speaker 2: vector protocol. You enable it with router RIP, then tell
Speaker 2: it what networks to advertise YEP using the network command.
Speaker 2: But crucially with RP version one and sometimes version two,
Speaker 2: you use the classical network number like network one nine
Speaker 2: two point one six eight point one one point zero,
Speaker 2: even if you're using subnets within.
Speaker 1: That class four. Okay.
Speaker 2: Version two is better supports subnet masks. It's common to
Speaker 2: use version two and no auto summary to stop it
Speaker 2: from doing unhelpful classful summarization. You might also use passive
Speaker 2: interface on interfaces facing users, so RIT updates don't go
Speaker 2: out there and troubleshooting debug IP RIP shows you the
Speaker 2: updates being sent or received. Also show a protocols gives
Speaker 2: you info about RIP timers and settings.
Speaker 1: Got it next up E I g RP E I g.
Speaker 2: RP Enhanced Interior Gateway Routing Protocol Cisco proprietary but very popular.
Speaker 2: It's an advanced distance sometimes called hybrid.
Speaker 1: How do you turn it on?
Speaker 2: Router I GRIP followed by an autonomous system number like
Speaker 2: router I GRIP one hundred. This as number must match
Speaker 2: on all routers you want to become neighbors.
Speaker 1: Okay, as number is key. What else?
Speaker 2: EIGRP uses metrics based on bandwidth and delay. By default,
Speaker 2: the bandwidth command on interface influences the calculation, but doesn't
Speaker 2: actually change the interface speed. It supports unequal cost load
Speaker 2: balancing using the variance command. Like RIP, no auto summary
Speaker 2: is usually recommended.
Speaker 1: What about security?
Speaker 2: EIGRP has robust MT five authentication. You create a key chain,
Speaker 2: define key numbers and key string passwords and apply it
Speaker 2: to the interface and choos. Routers only accept updates from
Speaker 2: trusted neighbors. Very important o'ifying EIGRP show at P c
Speaker 2: rep neighbors to see adjacent routers, show apic GRIP topology,
Speaker 2: shows the routes. EIGRP knows about debug I GRIP packets
Speaker 2: for deep troubleshooting.
Speaker 1: Cool and finally, OSPF.
Speaker 2: OSPF Open Shortest Path first industry standard link state protocol
Speaker 2: very scalable wide use.
Speaker 1: How it's a configure router OS.
Speaker 2: Followed by a process eight like router os one. This
Speaker 2: idea is just locally significant. It doesn't have to match
Speaker 2: between routers.
Speaker 1: Okay, different from eigrp's AS number.
Speaker 2: Right. Then you use the network command. But it's different
Speaker 2: here network IP address, wildcard mask, area, area card mask.
Speaker 1: What's that?
Speaker 2: It's like an inverted subnet maask zeros mean match this
Speaker 2: bit exactly, ones mean ignore this bit. So network one
Speaker 2: ninety two point one six eight point hero zero point
Speaker 2: two five to five. Area zero means enable OSPF on
Speaker 2: any interface whose IP starts with a one ninety two
Speaker 2: point one sixty eight point one. The area is crucial
Speaker 2: for osps's hierarchical design.
Speaker 1: And loopback interfaces are important.
Speaker 2: Often use for the routar eight. OSPF needs a unique
Speaker 2: ID for each router. A loopback interface IP is stable
Speaker 2: because it never goes down unless manually shut down, making
Speaker 2: it a good source for the router ID. What else
Speaker 2: is key for OSPF on multi access networks like ethernet,
Speaker 2: OSPF ALEXA designated router DR and backup DR. To manage adjacencies,
Speaker 2: you can influence this with EPUS five priority on the
Speaker 2: interface priority wins Priority zero means it can't become DRBDR.
Speaker 2: OSPF uses cost calculated from interface bandwidth. Lower cost is
Speaker 2: better higher band with lower cost. Authentication is also supported.
Speaker 2: Simple textor MD five and OSBF timers the hello interval
Speaker 2: and dead interval months match between neighbors for them to
Speaker 2: form an.
Speaker 1: Adjacency verifying OSPF show.
Speaker 2: IP your ref of neighbor is key, show IP ASP
Speaker 2: of database shows the link state information, debug APAASP events
Speaker 2: helps troubleshoot adjacency issues. OSPF is powerful, especially in larger
Speaker 2: complex networks.
Speaker 1: Okay, that's a whirlwind tour of routing. Let's switch gears.
Speaker 1: Now move from the wide area network down to the
Speaker 1: local network switches.
Speaker 2: Right connecting devices within the same building or floor, typically
Speaker 2: managing local traffic.
Speaker 1: Switches have modes like routers too, YEP user.
Speaker 2: Mode, switch, privileged mode, switch, hashtag, global config. Very similar
Speaker 2: feel it is show commands many of the same show version,
Speaker 2: show running canfig but also switch specific ones like showflan,
Speaker 2: showmac address table, show interfaces status.
Speaker 1: How do you configure basic switch info?
Speaker 2: Pretty much like a router hostname name to say, the team.
Speaker 2: Password configuration is identical. Enable secret line console, zero line
Speaker 2: vt AoE fifteen switches often to have more vty lines,
Speaker 2: password log in service, password encryption.
Speaker 1: Can you give us switch an IP address? I thought
Speaker 1: there were layer two devices?
Speaker 2: Good question. They operate primarily at layer two. Yes, forwarding
Speaker 2: based on AIRP addresses. But for management, so you can
Speaker 2: telnet or SSH into the switch, you need an IP
Speaker 2: address where you can figure that on a switched virtual
Speaker 2: interface or SVII, usually interface FLAN one. By default, you
Speaker 2: go to that interface, assign an app address of address,
Speaker 2: subnet mask and no shutdown. You also need to configure
Speaker 2: a default gateway for the switch using I Default Gateway
Speaker 2: Gateway IP in global CONFIGU mode, so you can reach
Speaker 2: management stations on other networks.
Speaker 1: Huh okay, so the IP is just for managing the
Speaker 1: switch itself exactly.
Speaker 2: You can also set interface descriptions, configure speed in duplex settings.
Speaker 2: Auto is common, but sometimes you need to hard code them.
Speaker 1: And resetting a switch reload.
Speaker 2: Restarts it right. A restartup config wipes the safe config
Speaker 2: but wiping VLAN infos different. You need to erase flash
Speaker 2: dot vland DOTU. Careful with that command, very careful, make
Speaker 2: sure you type the call incorrectly. Flash dot vland dot
Speaker 2: dot dat. If you just do a race flash, you
Speaker 2: could wipe the entire operating system.
Speaker 1: Hikes. Okay, Switches work with MPO addresses, right, How do
Speaker 1: you manage those?
Speaker 2: They learn app addresses automatically by looking at the source
Speaker 2: address of frames coming into each port. They build a
Speaker 2: macaddress table sometimes it's called a CAM table. You can
Speaker 2: see it with show Mac address table.
Speaker 1: Can you clear it?
Speaker 2: Yep? Clear macaddress table. Dynamic removes all learned addresses. Or
Speaker 2: you can specify an interface or VLAN.
Speaker 1: Can you manually assign a MAC address to a port?
Speaker 2: You can mac address table static macaddress landed interface type number.
Speaker 2: This permanently locks that MPOCK address to that specific port
Speaker 2: in that vland. Sometimes used for security or specific configurations.
Speaker 1: Speaking of security, what about locking down ports preventing random
Speaker 1: people from plugging.
Speaker 2: In AH port security crucial feature on switches Unless you
Speaker 2: control witch MACA addresses and how many are allowed to
Speaker 2: connect to a specific switch.
Speaker 1: Port, how do you turn it on?
Speaker 2: First, make sure the port is an access port, switchport
Speaker 2: mode access. Then switchport port security enables the feature on
Speaker 2: that interface.
Speaker 1: Then you set the rules exactly.
Speaker 2: Switchport port security maximum value says how many MAC addresses
Speaker 2: are allowed, often just one. Switchport port security mac address
Speaker 2: MAC address can statically define the allowed MAC or you
Speaker 2: can use switch court port security MAC address dicky to
Speaker 2: let the switch learn the first MA address it sees
Speaker 2: and stick it to the port.
Speaker 1: What happens if someone violates the rule plugs in a
Speaker 1: different device That depends.
Speaker 2: On the violation mode. You said it with switch port
Speaker 2: security violation shut down restrict.
Speaker 1: Protect shutdowns sounds serious.
Speaker 2: It is. The interface goes into an air disabled state,
Speaker 2: effectively shutting it down requires manual intervention to bring back
Speaker 2: ups drops the violate in traffic and sends log messages
Speaker 2: in S and MP traps. The port stays up, but
Speaker 2: the unauthorized device can't communicate. Protect simplest just drops the
Speaker 2: violating traffic, no logs port stays up. Shutdown is the
Speaker 2: most common secure default.
Speaker 1: How do you check if port security tripped?
Speaker 2: Show port security interface type number gives you all the details.
Speaker 2: Max addresses, current count, sticky ams, violation mode and security
Speaker 2: action count.
Speaker 1: Okay, very useful. Now let's talk VLANs virtual lands right.
Speaker 2: Breaking up one physical switch into multiple logical broadcast domains
Speaker 2: great for security organization performance.
Speaker 1: How do you create them?
Speaker 2: Simple? In global config land landed like land ten, then
Speaker 2: optionally name name like name sales.
Speaker 1: VLAN ten is now called sales. How do you put
Speaker 1: ports into it?
Speaker 2: Go into the interface canfig interface faster net zero one
Speaker 2: First make it an access port switchport mode access, then
Speaker 2: assign it switchboard access LAN ten, So.
Speaker 1: Fazero one is now in the sales vlan. Can you
Speaker 1: do multiple ports at once?
Speaker 2: Yes? Using the interface range their face range fasten it
Speaker 2: zero one ten than any commands you type applied to
Speaker 2: all ten ports. Very efficient. Verifying VLAN Chovelan brief is
Speaker 2: the best quick overview shows all vlands their names and
Speaker 2: which ports are assigned to them. You can also use
Speaker 2: chauvelin name sales or Chauvelan E ten.
Speaker 1: How are VLANs saved? Is it in the startup configure?
Speaker 2: Mostly? Yes? For standard range vilans one one thousand and five,
Speaker 2: they're actually saved in that VLAN dot dot file and
Speaker 2: flash memory we mentioned. Extended range villans one thousand and
Speaker 2: six four to ninety four might behave differently depending on
Speaker 2: the switch model and configuration.
Speaker 1: Mode and clearing VLAN assignments.
Speaker 2: On an interface no switch court access FLAN usually puts
Speaker 2: it back into VLAN one. The default to delete a
Speaker 2: vilan entirely use no VLAN ten, but be careful any
Speaker 2: ports still assigned to VLAN ten will become inactive. Best
Speaker 2: practice is to reassign the ports before deleting the VLAN
Speaker 2: good tip.
Speaker 1: Okay, Last big topic connecting switches together and managing VLANs
Speaker 1: across multiple switches. Trunking and BTP right.
Speaker 2: If you want multiple vlands to cross a link between
Speaker 2: two switches, you need a trunk, and VDP helps synchronize
Speaker 2: VLAN databases.
Speaker 1: How does a trunk get formed?
Speaker 2: Often automatically using DTP Dynamic trunking Protocol Cisco proprietary interface
Speaker 2: modes like Dynamic Auto or Dynamic Desirable negotiate, or you
Speaker 2: can manually force it with switchport mode. Trunk using switchport
Speaker 2: non negotiate turns off DTP if you hardcode it as
Speaker 2: a trunk or.
Speaker 1: Access port and the trunk needs to know how to
Speaker 1: tag the traffic for different vlands.
Speaker 2: Right, exactly. That's encapsulation. Two main types Cisco's old ISL
Speaker 2: and the industry standard IEE eight two point one Q
Speaker 2: often called DOT one Q. You can figure it with
Speaker 2: switchport trunk encapsulation is ATO dot one Q negotiate. Most
Speaker 2: modern networks use dot one Q if set to negotiate,
Speaker 2: it usually prefers isl Both sides support.
Speaker 1: It, okay, Now, VTP VLAN trunking protocol.
Speaker 2: This protocol lets one switch the VTP server manage the
Speaker 2: VLAN database for other switches VTP clients in the same
Speaker 2: VDP domain. You create VLAN twenty on the server and boom,
Speaker 2: it automatically appears on all the clients.
Speaker 1: Saves a lot of work.
Speaker 2: Huge time saver. In large networks, you can figure the
Speaker 2: VDP mode server client or transparent. Transparent switches manage their
Speaker 2: own vlands, but PASSVDP info. You said a VDP domain
Speaker 2: name and optionally a VTPU password password, then those have
Speaker 2: to match absolutely critical domain name and password must be
Speaker 2: identical case sensitive for switches to exchange VTP updates. A
Speaker 2: mismatch can cause big problems.
Speaker 1: What's VTP pruning smart feature?
Speaker 2: If enabled, VTP pruning switches tell their neighbors which VLANs
Speaker 2: they actually have active ports for. Then broadcast traffic for
Speaker 2: a specific VLAN is only sent across trunks if the
Speaker 2: neighboring switch actually needs that. VLAN reduces unnecessary.
Speaker 1: Traffic verifying VTP.
Speaker 2: So VTP status gives you the mode, domain name, revision number,
Speaker 2: very important pruning status, show VTP counters, shows update statistics.
Speaker 1: Wow, we've covered a ton of ground, from basic cables
Speaker 1: and ips all the way to complex routing and switching configus.
Speaker 2: We really have. It's the core toolkit for a CEC
Speaker 2: and a engineer.
Speaker 1: So what does this all mean for you listening? You've
Speaker 1: just gotten, hopefully a really powerful shortcut to understanding these
Speaker 1: cor Cisco commands and concepts. We've tried to unpack everything
Speaker 1: from you know, literally how devices connect to how they
Speaker 1: talk across networks and how you manage them.
Speaker 2: It really provides that foundational command structure. But this raises
Speaker 2: a final important question for you, yea, how will you
Speaker 2: take this structured knowledge, this theory and turn it into
Speaker 2: hands on practice?
Speaker 1: Right reading about it is one thing.
Speaker 2: Exactly We really recommend you get into simulation labs, packet tracer,
Speaker 2: GNS three, EVENG whatever works for you. Start typing these commands,
Speaker 2: build networks, break them, fix them. That's where the real
Speaker 2: learning happens, when you actually apply it