Lecture Notes For CCNA

CHAPTER 5 - Routing!

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RIP

config t, router rip, network 10.0.0.0, ^z

needs network x.x.x.x to tell it which net. to broadcast about, every 30 secs

RIP can only do classful routing, no subnet masks!

sh ip route shows rip entries with r next to them

sh ip route rip just shows rip...

debug ip rip shows lve rip updates

max 15 hops, not basedon cost etc.

IGRP

HANDLES LARGER NETWORKS

router irgp #  command

network x.x.x.x

# autonmous network number (16 bit) -- all routers with same no. exchange info.

== as = autonomous system

delay, mtu, bandwidth, reliability, load (see sh int s0)

maximumtransmission unit, bandwidth default is 1544 kbit (t1)

I in sh ip route is irgp entry

every 90 secs by default

sh ip protocol shows routing protocols, as no. etc.

topology changes

hop count - over 15 with rip kills packet = counting to infinity / ttl exceeded

split horizon

enforces rule that says routing info. cannot be sentback the way it came.

rout poisoning

enter down network as 16 = unreachable = infinite

therefore router does not listen to other routers saying net is up until it can see it, at which point it will tell it's neighbours

hold-downs

work with rout poisoning

prevents rapid change, allows downed route to come back up

triggered updates

hold down tme xpires

hold down timer receives update saying net status has changed

static routes

can also cause loop if bad!

ip route dest net subnet next hop addr metric

ip route 10.0.0.0 255.0.0.0 10.0.0.99 3

metric = weighting of link

benefits of us in routers to segment network

manageability

inceased functionality

multipleactive paths

broadcasts not forwarded