• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 312
  • Last Modified:

Ripv2 question (easy)

This is debug output:

3w1d: RIP: sending v2 update to 224.0.0.9 via Ethernet0/0 (192.168.2.5)
3w1d: RIP: build update entries
3w1d:   192.168.3.0/24 via 0.0.0.0, metric 1, tag 0
3w1d:   192.168.4.0/24 via 0.0.0.0, metric 1, tag 0
3w1d: RIP: sending v2 update to 224.0.0.9 via Ethernet0/0.1 (192.168.3.1)
3w1d: RIP: build update entries
3w1d:   192.168.2.0/24 via 0.0.0.0, metric 1, tag 0
3w1d:   192.168.4.0/24 via 0.0.0.0, metric 1, tag 0
3w1d:   192.168.6.0/24 via 0.0.0.0, metric 2, tag 0
3w1d: RIP: sending v2 update to 224.0.0.9 via Ethernet0/0.2 (192.168.4.1)
3w1d: RIP: build update entries

This is on a 2600 router w/sub interfaces obviously.
Networks attached are   192.168.2.0/28   192.168.3.0/28  and 192.168.4.0/28

1. The thing I dont understand, is the "RIP: BUILD UPDATE ENTRIES" field. What does this mean?

2. Also: 192.168.2.0, 192.168.4.0 and 192.168.6.0 do NOT have a /24 mask. Why are they showing up as /24 ???  Is this Ripv2 doing summarization?
0
dissolved
Asked:
dissolved
  • 8
  • 7
1 Solution
 
dissolvedAuthor Commented:
heres a sh ip ro of the router


     192.168.4.0/28 is subnetted, 1 subnets
C       192.168.4.0 is directly connected, Ethernet0/0.2
R    192.168.6.0/24 [120/1] via 192.168.2.3, 00:00:01, Ethernet0/0
     192.168.2.0/28 is subnetted, 1 subnets
C       192.168.2.0 is directly connected, Ethernet0/0
     192.168.3.0/28 is subnetted, 1 subnets
C       192.168.3.0 is directly connected, Ethernet0/0.1
S*   0.0.0.0/0 [1/0] via 192.168.2.1
0
 
Don JohnstonInstructorCommented:
>1. The thing I dont understand, is the "RIP: BUILD UPDATE ENTRIES" field. What does this mean?

Before the routing update can be sent, it has to be created. The routing table is parsed and an update is built.

>2. Also: 192.168.2.0, 192.168.4.0 and 192.168.6.0 do NOT have a /24 mask. Why are they showing up as /24 ???

My guess is you have "auto-summary" still enabled. RIP will automatically summerize to the classful boundary. If you want it to send the REAL mask, issue the "no auto" command from with the rip routing protocol config. (only works in Version 2 mode, though.)

-Don
0
 
dissolvedAuthor Commented:
Hi again Don:

1. so the "no auto" command stops Ripv2 from sending a classful mask. Just by issuing "no auto"  will make it start advertising the REAL mask? No other commands are needed right?

2. Does Ripv1 auto-summarize????
0
Ultimate Tool Kit for Technology Solution Provider

Broken down into practical pointers and step-by-step instructions, the IT Service Excellence Tool Kit delivers expert advice for technology solution providers. Get your free copy now.

 
Don JohnstonInstructorCommented:
Yes and no.

-Don
0
 
dissolvedAuthor Commented:
Ripv2 auto summarizes right?

Ripv1 just summarizes to whatever the default mask is. This is just it's natural behavior, it's not "auto-summary" ???
0
 
Don JohnstonInstructorCommented:
Oops. Disregard the previous...

Yes and Yes.

-Don
0
 
Don JohnstonInstructorCommented:
RIP v1 and v2 both auto summerize by default. With v2, you can disable summerization.

RIP v1 always summerizes to the classful boundry and you can't deiable it.

-Don
0
 
dissolvedAuthor Commented:
thanks !
0
 
dissolvedAuthor Commented:
Interesting...
I am running EIGRP and Ripv2 on this router. When EIGRP was on, all I saw was a "D."  Never say RIP.

 However, when I disabled auto-summary in my router config, RIP started showing up in my routing table. Is this normal?  Or just coincidence?


     192.168.4.0/24 is variably subnetted, 2 subnets, 2 masks
D       192.168.4.0/24 is a summary, 01:23:29, Null0
C       192.168.4.0/28 is directly connected, Ethernet0/0.2
     192.168.6.0/24 is variably subnetted, 3 subnets, 3 masks
R       192.168.6.2/32 [120/1] via 192.168.2.3, 00:00:05, Ethernet0/0
R       192.168.6.0/30 [120/1] via 192.168.2.3, 00:00:05, Ethernet0/0
D       192.168.6.0/24 [90/2195456] via 192.168.2.3, 01:22:30, Ethernet0/0
     192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks
D       192.168.2.0/24 is a summary, 01:23:35, Null0
C       192.168.2.0/28 is directly connected, Ethernet0/0
     192.168.3.0/24 is variably subnetted, 2 subnets, 2 masks
D       192.168.3.0/24 is a summary, 01:23:35, Null0
C       192.168.3.0/28 is directly connected, Ethernet0/0.1

Before these were just all Ds and Cs
0
 
Don JohnstonInstructorCommented:
Yes and yes.

When RIPv2 and EIGRP were running, you were learning the same /24 routes through two different routing protocols. When you learn the same network through two different protocols, administrative distance determines which get placed into the routing table. Since EIGRP has an AD or 90 and RIP is 120, the "D" routes are entered into the routing table.

When you disabled auto-summerization, the router began seeing the /28 routes. Because you hadn't disabled EIGRP's auto-summerization, those /28 routes were only being learned through RIP.

Notice though, that you're still seeing the /24 routes through EIGRP? That's because they aren't being advertised by RIP anymore.

-dj
0
 
dissolvedAuthor Commented:
So Rip is not summarizing anymore. Which is why the real masks are being shown.
EIGRP is still summarizing.

One thing I am confused about is:
>>>When you disabled auto-summerization, the router began seeing the /28 routes. Because you hadn't disabled EIGRP's auto-summerization, those /28 routes were only being learned through RIP>>>

Since EIGRP is still enabled, why didnt it take over and start routing for the /28 routes?

thanks a lot man
0
 
Don JohnstonInstructorCommented:
> So Rip is not summarizing anymore. Which is why the real masks are being shown.

Yep

>Since EIGRP is still enabled, why didnt it take over and start routing for the /28 routes?

Because, like RIPv2, auto-summerization is enabled by default. If you disable it... Go ahead, I'll wait. Then you'll see the R routes get replaced by the D routes.

-dj
0
 
dissolvedAuthor Commented:
Thanks for help. I will play with the protocols tonight. I will post a new question I'm sure. I still do not fully understand why turning off summarization lets another routing protocol take over. ie: when I disabled Rip auto-summary, IGRP took control of some of the routes.  I dont understand what administrative distance or metric has to do with summarization I guess.

thanks again
0
 
Don JohnstonInstructorCommented:
Admin Distance is a way of figuring out the "best" route to a network if you learn it through more than one protocol.

Put yourself in the router's position: You learn about the 172.16.0.0 network from RouterA telling you it's 3 hops away (RIP). A second or two later, you hear about from RouterB telling you it's 32456 away (IGRP). Because the two routing protocols have TOTALLY different methods of expressing "how far away" a network is, you need another method to figure out which one of these you're going to put in your routing table.

Administrative Distance...

RIP = 120 (sucks)
OSPF = 110 (Actually should be 80)
IGRP = 100 (better)
EIGRP = 90 (best)

So if you were hearing about the 172.16.0.0 network from four different routers, each one using a different protocol, the only one you'd see is the EIGRP route. Because it has the lowest AD.

-Don
0
 
dissolvedAuthor Commented:
thanks for the help Don. Rather than continue to post here, I made new questions. If you have time, can you take a look at them for me?

Thanks again

http://www.experts-exchange.com/Hardware/Routers/Q_21404334.html

http://www.experts-exchange.com/Hardware/Routers/Q_21404329.html
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Ultimate Tool Kit for Technology Solution Provider

Broken down into practical pointers and step-by-step instructions, the IT Service Excellence Tool Kit delivers expert advice for technology solution providers. Get your free copy now.

  • 8
  • 7
Tackle projects and never again get stuck behind a technical roadblock.
Join Now