Can somebody please clear this up for me, RIP Question

Futura · March 2011

I understand that Rip V1 classfull which it must be either /8 /16 or 24/ but V2 can be classless so how does rip V2 know what the mask is? does it go of the interface ip settings?

Also can V1 ever have a /27 etc or does this just not work?

Also, when advertising networks, is it true that you must just 'always' advertise the classfull address ie

network 192.168.1.0 - 192.168.255.0
network 172.16.0.0 - 172.31.0.0
network 10.0.0.0

Does this go for V1 and V2?

I have watched train signal vidoes and Chris Bryant advertises 172.16.123.0 via Rip and its contrary to what I've read already.

Many thanks, I have ICND 1 on wednesday so want to be sure.

thedrama · March 2011

Futura wrote: »

I understand that Rip V1 classfull which it must be either /8 /16 or 24/ but V2 can be classless so how does rip V2 know what the mask is? does it go of the interface ip settings?

Also can V1 ever have a /27 etc or does this just not work?

Also, when advertising networks, is it true that you must just 'always' advertise the classfull address ie

network 192.168.1.0 - 192.168.255.0
network 172.16.0.0 - 172.31.0.0
network 10.0.0.0

Does this go for V1 and V2?

I have watched train signal vidoes and Chris Bryant advertises 172.16.123.0 via Rip and its contrary to what I've read already.

Many thanks, I have ICND 1 on wednesday so want to be sure.

Hey mate what you should do only is disabling auto-summary. And you can
do this by no auto-summary command typed under your directly connected
networks.(Networks advertised by you)

capitanuionut · March 2011

thedrama wrote: »

Hey mate what you should do only is disabling auto-summary. And you can
do this by no auto-summary command typed under your directly connected
networks.(Networks advertised by you)

From what i know so far, RIPv1 is a classfull rounting protocol, so it sumarizes the IP addresses to the classfull in the routing table, it doesn't include subnet mask in routing updates, and does not support VLSM.

RIPv2 includes the subnet mask in the routing updates, this means that it supports VLSM.

yapchinhoong2010 · March 2011

I have similar doubt when studying about RIPv1. RIPv1 actually somehow supports VLSM, provided that the same subnet mask is being used throughout the whole network.

Have a look on the following blog post:
- itcertnotes -: RIPv1 and VLSM

capitanuionut · March 2011

yapchinhoong2010 wrote: »

I have similar doubt when studying about RIPv1. RIPv1 actually somehow supports VLSM, provided that the same subnet mask is being used throughout the whole network.

Have a look on the following blog post:
- itcertnotes -: RIPv1 and VLSM

You are not right!
Ripv1 clearly does not support VLSM, it pus the info in its routing table, using the subnet mask of the interface that received the update. That's why in that posting he said that he needs 16 equal subnets with /28. If ripv1 supported VLSM then for the WAN links would be for sure a /30 subnet mask.

okplaya · March 2011

yapchinhoong2010 wrote: »

RIPv1 actually somehow supports VLSM, provided that the same subnet mask is being used throughout the whole network.

When the same subnet mask is being used there is no variance. VLSM means that you CAN use different subnet masks. In your example the same subnet mask is being used throughout.

alan2308 · March 2011

Futura wrote: »

I understand that Rip V1 classfull which it must be either /8 /16 or 24/ but V2 can be classless so how does rip V2 know what the mask is? does it go of the interface ip settings?

Also can V1 ever have a /27 etc or does this just not work?

RIPv2 advertises the subnet mask of each route along with the network number. In the RIPv1 packet, each network is followed by an unused field that must be all 0's, but in RIPv2, this field is used for the subnet mask.

With RIPv1, the router can make assumptions based on attached networks. For example, if one of the interfaces is connected to 172.16.1.0/24, then it will assume that all 172.16.x.x networks it receives in RIPv1 advertisements also have a /24 subnet mask. You cannot have variable length masks, and you cannot have discontiguous networks.

Futura wrote: »

Also, when advertising networks, is it true that you must just 'always' advertise the classfull address ie

network 192.168.1.0 - 192.168.255.0
network 172.16.0.0 - 172.31.0.0
network 10.0.0.0

Does this go for V1 and V2?

I have watched train signal vidoes and Chris Bryant advertises 172.16.123.0 via Rip and its contrary to what I've read already.

What you type into the RIP configuration with the network command is not simply what you're advertising. The network command is used to specify which interfaces are to participate in the RIP process. If you type, for example, network 10.0.0.0, then every interface that falls within the classful 10.0.0.0 network will participate in the RIP process. So if you have 10.0.0.0/24, 10.1.0.0/16 and 10.2.2.0/30, then RIP will send and receive updates on those interfaces and include those networks in it's routing update.

Futura · March 2011

I'm thinking in terms of exam questions.

If it was a network like 172.16.1.0

should i type

router rip
version 2
network 172.16.0.0 classfull
or
network 172.16.1.0 classless

Many thanks?

alan2308 · March 2011

Which ever way you type it in (172.16.0.0 or 172.16.1.0) it will end up in your configuration as 172.16.0.0. Short answer, go classful.

CodeBlox · March 2011

Discontiguous networks is a problem with RIPV1. No support for VLSM and all Mask should be the same (SLSM). The only subnet information with RIPV1 is assumed at the interface. RIPv1 config below:

Router#sh ip ro
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

[COLOR=RED][B]     172.16.0.0/19 is subnetted, 3 subnets
R       172.16.0.0 [120/1] via 172.16.95.254, 00:00:07, Serial0/0/0
                   [120/1] via 172.16.32.1, 00:00:00, Serial0/0/1[/B]
[/COLOR]
C       172.16.32.0 is directly connected, Serial0/0/1
C       172.16.64.0 is directly connected, Serial0/0/0
Router#
Router#sho ip proto
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 3 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: rip
Default version control: send version 1, receive 1
  [COLOR=RED][B]Interface             Send  Recv  Triggered RIP  Key-chain
  Serial0/0/0           1     1     
  Serial0/0/1           1     1     
Automatic network summarization is not in effect
[/B][/COLOR]
Maximum path: 4
Routing for Networks:
    172.16.0.0
Passive Interface(s):
Routing Information Sources:
    Gateway         Distance      Last Update
    172.16.95.254        120      00:00:06
    172.16.32.1          120      00:00:10
Distance: (default is 120)

Edit: Didn't read entire thread: You would need to type classful boundary. All interfaces that belong to that boundary will be advertised: EX "network 172.16.0.0" or "network 10.0.0.0"

Can somebody please clear this up for me, RIP Question

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