RIP Question

zobo88

When you add a network in RIP than does it means that you are activating the broadcast at all interfaces of this router that this route x.x.x.x is connected to me ?

suppose we have a router A which is connected to network A and Network B
and I issue command network A under router rip, so will this also start sending broadcasts about the availability of network A from interface of Network B ?

sandman748

rip will advertise out all active interfaces unless you specifically tell it which interfaces not to advertise out of.

hexem

under rip subconfiguration mode

passive-interface serial0

The interface will still listen for broadcast's but won't send updates out on that interface.

zobo88

sandman748 wrote: »

rip will advertise out all active interfaces unless you specifically tell it which interfaces not to advertise out of.

do you mean to say that there is no need to specify networks using network x.x.x.x commands ? we just need to issue router rip and all will be set ?

johnwest43

After you issue router rip you need to tell the router which networks to advertise by using the
network xxx.xxx.xxx.xxx command. by default this will advertise network xxx.xxx.xxx.xxx out all interfaces. When you issue the passive-interface s0 command this tells the router to advertise the route out every interface except s0.

To answer your question, no. You still need to use the network command to specify which networks you want to advertise.

I hope this helps!!

John

zobo88

thanks John, it clear up a loy
and about reception of RIP updates? it gets enabled at all interfaces on just the issuance router rip command

zobo88

can anyone confirm about the reception of rip-updates ?

Forsaken_GA

johnwest43 wrote: »

After you issue router rip you need to tell the router which networks to advertise by using the
network xxx.xxx.xxx.xxx command. by default this will advertise network xxx.xxx.xxx.xxx out all interfaces. When you issue the passive-interface s0 command this tells the router to advertise the route out every interface except s0.

The better way to handle this is to issue the passive-interface default command in router rip mode to suppress routing updates on all interfaces by default. Then use the no passive-interface <int name> to allow routing updates on the interfaces you want to participate. Routing should always be something that's done on purpose, and you should eliminate any possibility of an interface accepting or sending routing updates that doesn't need to.

Forsaken_GA

zobo88 wrote: »

thanks John, it clear up a loy
and about reception of RIP updates? it gets enabled at all interfaces on just the issuance router rip command

passive interface only disables the sending of RIP updates, a passive interface will still receive RIP updates. This is important to note, because that's not the behavior of a passive interface under EIGRP/OSPF, passive interface will disable the sending of hello packets, and so no adjacencies will form, but since RIP doesn't use adjacencies, it can still accept routing updates on it's passive interfaces.

and RIP is like OSPF, the network command just tells it what interfaces are participating in RIP. If the interface has an address that's within the range specified by your network command, rip will be enabled on that interface. RIP is not enabled on all interfaces automatically just because you typed router rip

zobo88

Forsaken_GA wrote: »

passive interface only disables the sending of RIP updates, a passive interface will still receive RIP updates. This is important to note, because that's not the behavior of a passive interface under EIGRP/OSPF, passive interface will disable the sending of hello packets, and so no adjacencies will form, but since RIP doesn't use adjacencies, it can still accept routing updates on it's passive interfaces.

and RIP is like OSPF, the network command just tells it what interfaces are participating in RIP. If the interface has an address that's within the range specified by your network command, rip will be enabled on that interface. RIP is not enabled on all interfaces automatically just because you typed router rip

oh that is again confusing, let me try to ask point by point

Rip will only listen to rip messages on networks and their associated interfaces which it is also advertising by rip ?

Rip will broadcast the rip messages on all networks and their associated interfaces which we define by netwrok x.x.x.x command ?

like if a router has three network
192.168.1.2 eth0
192.168.2.2 eth1
192.168.3.2 eth3
and we issue command
router ip
network 192.168.1.0
network 192.168.2.0

than the router will broadcast 192.168.1.0 and 192.168.2.0 only on eth1 and eth0, it won't be broadcasted on eth3 ?

and similarly for reception of rip updates from other router, the updates will be only accepted on eth0 and eth1 and no updates will be accepted at eth3

Forsaken_GA

zobo88 wrote: »

than the router will broadcast 192.168.1.0 and 192.168.2.0 only on eth1 and eth0, it won't be broadcasted on eth3 ?

and similarly for reception of rip updates from other router, the updates will be only accepted on eth0 and eth1 and no updates will be accepted at eth3

I'm not trying to be coy, but is this something you've attempted to lab up and see what the results are? That's the best way to answer your question

zobo88

Forsaken_GA wrote: »

I'm not trying to be coy, but is this something you've attempted to lab up and see what the results are? That's the best way to answer your question

I only have simulator and from there I think that router will only send and receive rip updates only from the networks and their connected interfaces for which we issue the network x.x.x.x command
but I am not sure and that is why I have asked at the forums for clarification

so as per my test if a router has three network
192.168.1.2 eth0
192.168.2.2 eth1
192.168.3.2 eth3
and we issue command
router ip
network 192.168.1.0
network 192.168.2.0

than the router will broadcast 192.168.1.0 and 192.168.2.0 only on eth1 and eth0, it won't be broadcasted on eth3 , now this is in contarst to what johnwest43 has told above

and similarly for reception of rip updates from other router, the updates will be only accepted on eth0 and eth1 and no updates will be accepted at eth3

hexem

The network statement tell's rip what network's to advertise and which interfaces are to send/receive updates.

so yes if you don't put a network statement for 192.168.3.0 that interface will not send receive/updates.

passive-interface however is used when you don't want to send updates out on that interface but advertise that network on others.

you can confirm all this using 'show ip protocols'

mikej412

The use of the network statement and the passive interface command might be more obvious if you lab up an example that includes networks that aren't on classful boundaries.

R1#show ip int brief | exc unset
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 10.0.1.1 YES manual up up
FastEthernet0/1 10.0.2.1 YES manual up up
FastEthernet2/0 10.0.3.1 YES manual up up
FastEthernet2/1 192.168.1.1 YES manual up up

R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#network 192.168.1.0
R1(config-router)#network 10.0.1.0
R1(config-router)#network 10.0.2.0
R1(config-router)#end
R1#wr

All the networks are configured with a /24 netmask and only the network statements above were configured..... yet

R1#show run | section router rip
router rip
version 2
network 10.0.0.0
network 192.168.1.0
R1#

and

R1#show ip protocol
*** IP Routing is NSF aware ***

Routing Protocol is "rip"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Sending updates every 30 seconds, next due in 19 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Redistributing: rip
Default version control: send version 2, receive version 2
Interface Send Recv Triggered RIP Key-chain
FastEthernet0/0 2 2
FastEthernet0/1 2 2
FastEthernet2/0 2 2
FastEthernet2/1 2 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
10.0.0.0
192.168.1.0
Routing Information Sources:
Gateway Distance Last Update
Distance: (default is 120)

FastEthernet2/0 is running RIP and advertising the 10.0.3.0 network even though I didn't type in the 10.0.3.0 network statement.

I explicitly configured version 2, and explicitly typed in the two network statements for the 10.0.1.0 and 10.0.2.0 networks, yet the classful network 10.0.0.0 is what showed up in the configuration.

While you could just enter the passive interface for the FA2/0 interface, setting passive interface as the default prevents any other interface from "accidentally" running RIP if it's configured with an IP address in the 10.0.0.0/8 range.

R1#show run | section router
router rip
version 2
passive-interface default
no passive-interface FastEthernet0/0
no passive-interface FastEthernet0/1
no passive-interface FastEthernet2/1
network 10.0.0.0
network 192.168.1.0
R1#

R1#show ip protocol
*** IP Routing is NSF aware ***

Routing Protocol is "rip"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Sending updates every 30 seconds, next due in 18 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Redistributing: rip
Default version control: send version 2, receive version 2
Interface Send Recv Triggered RIP Key-chain
FastEthernet0/0 2 2
FastEthernet0/1 2 2
FastEthernet2/1 2 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
10.0.0.0
192.168.1.0
Passive Interface(s):
Serial1/0
Serial1/1
Serial1/2
Serial1/3
Passive Interface(s):
Serial1/4
Serial1/5
Serial1/6
Serial1/7
FastEthernet2/0
VoIP-Null0
Routing Information Sources:
Gateway Distance Last Update
Distance: (default is 120)

R1#

Attach another router running RIP on the the same network as R1's FastEthernet2/0 and check if it receives all the RIP routes from R1 before and after the passive interface command. You can also have a loopback interface configured and advertised to see if R1 receives it both before and after the passive interface command on R1. You should also check the routing table on that router before and after the passive interface command on R1 -- when do you receive the network advertisements from R1 and when do they stop?

zobo88

Thanks Mike
but it is a bit confusing
Since we are using rip 2 which does carry the class information than why do the 10.0.1.0 and 10.0.2.0 networks get rounded as 10.0.0.0 ? and why is a /8 mask carried in routing updates?

notgoing2fail

zobo88 wrote: »

Thanks Mike
but it is a bit confusing
Since we are using rip 2 which does carry the class information than why do the 10.0.1.0 and 10.0.2.0 networks get rounded as 10.0.0.0 ? and why is a /8 mask carried in routing updates?

Good question. It's because RIPv2 has autosummarization. You have to turn it off.

Automatic network summarization is in effect


Just type this:

no auto-summary

zobo88

so If we are using Ripv2 with auto summarization than it more or less just becomes Ripv1 ? as the main difference between Ripv2 and v1 is classful/classless routing ?

or is there something more which I am missing?

EMcCaleb

zobo88 wrote: »

Thanks Mike
but it is a bit confusing
Since we are using rip 2 which does carry the class information than why do the 10.0.1.0 and 10.0.2.0 networks get rounded as 10.0.0.0 ? and why is a /8 mask carried in routing updates?

Zobo, based on what Mike has shown, /8 will not be advertised (assuming auto-sum is off). On your sim you can lab up what Mike did and then debug IP rip to confirm.

Think of RIP as the little engine thats just doing the best it can. In its heart its just a little ole protocol trying to make it in this world. Yes, it truncates network statements to their classful boundries. However, it's still pulling the mask off the interface (just like OSPF, EIGRP).

As many others have said on this thread, the network statement is telling the router what interfaces to include in the process. Its NOT showing/displaying how the networks will be advertised.
HTH

notgoing2fail

zobo88 wrote: »

so If we are using Ripv2 with auto summarization than it more or less just becomes Ripv1 ? as the main difference between Ripv2 and v1 is classful/classless routing ?

or is there something more which I am missing?

Another good question. There are still some features of RIPv2 that separates it from RIPv1, so with auto-summary, I suppose it is in a way classful because it doesn't advertise the prefix.

I hope others can chime in a bit more.


RIPv2 uses multi-cast for updates, whereas RIPv1 uses broadcast I believe...so that's something that makes RIPv2 still unique...

EMcCaleb

zobo88 wrote: »

so If we are using Ripv2 with auto summarization than it more or less just becomes Ripv1 ? as the main difference between Ripv2 and v1 is classful/classless routing ?

or is there something more which I am missing?

Don't forget that RIPv2 uses multicast by default, its a large distinction. In this thread you've been refering to "broadcast". Ripv2 also supports authentication.

billyr

zobo88 wrote: »

do you mean to say that there is no need to specify networks using network x.x.x.x commands ? we just need to issue router rip and all will be set ?

If you lab this up you will see that RIP does not advertise out all active interfaces. It will advertise out of interfaces that are included with the network command.

A debug ip rip will confirm this.

The passive interface command is used for example in a situation where you still want to advertise a network to everyone with rip, but you do not want rip packets leaving out that network interface. e.g you have an interface with a switch attached to it - no point rip updates travelling out that interface every 30 seconds if there is no one to receive them, but you would still like other routers to know about that network.

Apologies if already stated, haven't read the whole thread, had a few beers while waiting for David Haye to smash up Ruiz. :0)