RIP versus directly connected

altdrugz

Hey, I have a single question for you :P. I saw that after configuring the RIP advertise in the serial interfaces of R1 and R2 (they are also directly connected ofcourse) in the show ip route output I do not see the "R" link. Ofcourse I see the directly connected thing.
My scenario: If I remember well this has to do with the Administrative Distance factor... When a link exists (with the same prefixes) in another way (rip for me in my case) it is not showing up (because it is not in use cause of the greater AD) until it goes down and uses the next route with the greater AD. Am I right? The tricky thing is the fact that R1 debug output shows that it sends the advertised route (of the serial link) BUT in R2 debug doesnt look like it has been received (?!).

zrockstar

What do you mean by it hasn't been received? Can you post some debug output? Remember, RIP will send all its routes every 30 seconds, it is up to the receiving router which routes it will install based off of already have a route with a lower AD or not.

altdrugz

Ok this is gonna be a bit big :P
from R1 perspective: (R1 serials ip 172.30.10.1 /16)

*Sep 13 13:31:04: RIP: sending v2 update to 224.0.0.9 via FastEthernet0/0 (172.21.1.1)*Sep 13 13:31:04: RIP: build update entries
*Sep 13 13:31:04: 172.30.0.0/16 via 0.0.0.0, metric 0, tag 0
*Sep 13 13:31:05: RIP: sending v2 update to 224.0.0.9 via Serial0/0/0 (172.30.10.1)
*Sep 13 13:31:05: RIP: build update entries
*Sep 13 13:31:05: 172.21.0.0/16 via 0.0.0.0, metric 0, tag 0
R1#u all
All possible debugging has been turned off
R1#show ip route


Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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


C 172.30.0.0/16 is directly connected, Serial0/0/0
C 172.21.0.0/16 is directly connected, FastEthernet0/0


R1#

R2's point of view :P

Gateway of last resort is not set

C 172.30.0.0/16 is directly connected, Serial0/0/1
C 172.31.0.0/16 is directly connected, FastEthernet0/0
R 172.21.0.0/16 [120/1] via 172.30.10.1, 00:00:08, Serial0/0/1


R2#
R2#debug ip rip
RIP protocol debugging is on
R2#
R2#
*Sep 13 13:33:40: RIP: sending v2 update to 224.0.0.9 via Serial0/0/1 (172.30.10.2)
*Sep 13 13:33:40: RIP: build update entries - suppressing null update


*Sep 13 13:33:40: RIP: recieved v2 update from 172.30.10.1 on Serial0/0/1
*Sep 13 13:33:40: 172.21.0.0/16 via 0.0.0.0 in 0 hops


*Sep 13 13:34:11: RIP: sending v2 update to 224.0.0.9 via Serial0/0/1 (172.30.10.2)
*Sep 13 13:34:11: RIP: build update entries - suppressing null update


*Sep 13 13:34:11: RIP: recieved v2 update from 172.30.10.1 on Serial0/0/1
*Sep 13 13:34:11: 172.21.0.0/16 via 0.0.0.0 in 0 hops


R2#u all
All possible debugging has been turned off
R2#

zrockstar

Sorry, I guess I am not understanding what the issue is here?

altdrugz

The fact that R1 - R2 serial link isnt showing in "show ip route" command as RIP.

vinbuck

Remember the routing table only shows the best route for a subnet. Each of the dynamic routing protocols will maintain it's own topology and offer that route to the routing table. If the route offered by the RIP database is the best route available, it will show an "R" next to it - if not, the routing table won't add it and use the current best route for the subnet. You are correct in your assumption that the AD is factoring in here.

So if you don't see it in the routing table, how do you verify that RIP is learning routes from another router?

Hint: show ip ..........

altdrugz

show ip proto

? :P Well definately both sides are advertising it.

R1 :

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 30 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
Serial0/0/0 2 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
172.21.0.0
172.30.0.0
Routing Information Sources:
Gateway Distance Last Update
Distance: (default is 120)


R1#

R2:

outing 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
Serial0/0/1 2 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
172.30.0.0
Routing Information Sources:
Gateway Distance Last Update
172.30.10.1 120 00:00:18
Distance: (default is 120)

So @vinbuck .. The reason that it doesnt show the rip link is the fact that its not the "best" path instead of the "directly connected" right (cause of AD)?

EV42TMAN

directly connected > static routes > rip/routing protocols

if you want to see rip in action with only 2 routers pick one of them and set up another network on the Fast Ethernet port
so for an example:
R1:
Serial0/0/1: 172.30.10.0 network
Fast Ethernet0/0: 192.168.0.0 network
R2:
Serial0/0/1: 172.30.10.0 network

In this example you'll see the 192.168.0.0 network as a RIP route on router 2 because you have to go through router 1 to get to it

if you want to take it as step further add 192.168.1.0 to the Fast Ethernet port on the Second router. then on the first router you should see 192.168.1.0 on the first router as well

vinbuck

altdrugz wrote: »

? :P Well definately both sides are advertising it.

R1 :


R2:


So @vinbuck .. The reason that it doesnt show the rip link is the fact that its not the "best" path instead of the "directly connected" right (cause of AD)?

Right! Here is the breakdown...

AD for Directly Connected is 0
AD for RIP is 120

AD is only evaluated if two routes are identical and the lowest wins...if they tie, it will load balance up to 4 routes by default (16 max)

The show command I was going to have you try is

show ip rip database

altdrugz

Thanx everyone
EV42TMAN Thats exactly what i have done! If you watched carefully my post you will see that the only rip route that exists is from the fast ethernet of R1.

vinbuck Altough load balancing isnt in ccna (or is it? im prepairing myself for CCENT atm..) but when you say 4 channels what you mean? If there is for example a rip path to R2 with an alternate path cost of 0 what is gonna happen? :P

PS: The

show ip rip database

isnt right in my 12.4(7) IOS that i play with. Actually it has no "rip" option after the show ip to me...

mapletune

altdrugz wrote: »

Altough load balancing isnt in ccna (or is it? im prepairing myself for CCENT atm..)

load balancing is not in the CCENT, i don't think so, you might want to recheck.

however, it is in the CCNA. You'll have to know about the differences between load balancing using different routing protocols. The biggest difference is that EIGRP can use "unequal cost load balancing" while the rest can only load balance over costs of "equal cost".

If you follow study materials closely, you'll get there when you get there no need to worry about it.

As for sh ip rip database... I think that only works for sh ip ospf database, and for eigrp it's sh ip eigrp topology. You'll be able to see ospf lsa's and eigrp feasible successors this way. Again, CCNA material, not CCENT.

RIP doesn't have a database because it's designed to advertise the whole routing table, parse it, select best, and that's it.

Cheers,
Mike

NetworkVeteran

mapletune wrote: »

As for sh ip rip database... RIP doesn't have a database because it's designed to advertise the whole routing table, parse it, select best, and that's it.

RIP does indeed have a database, and the protocol's a bit more complicated than that.

RIP doesn't advertise all the routes in the routing table, only the ones designated by the "network" command, those redistributed in, its summaries, and sometimes a default. There are refinements and exceptions to the above, but that's a good first cut.

(It's actually, imho, an interesting protocol to observe and troubleshoot!)