simple question

[rodney.adams]

I feel stupid for even asking this, but I'm stuck so here goes. I have a simple point-to-point T1 connection. I have a 1721 on one side and a 2620 on the other. I have the routers talking to each other, but I cannot get traffic from the two networks to pass through the routers. I have a route setup on each of the routers pointing the other way, what am I missing? Any help is appreciated.

[scottmac]

It would be very helpful if you would post your (sanitized, if necessary) configs.

Thanks

Scott

[ankurbhasin]

HI Rodney,

We all are waiting for your "sh run" and "sh ip route" from both the routers!!

Ankur

[rodney.adams]

Attached are the two configs.

[ankurbhasin]

Hi Rodney,

I cannot see any attachments. Try to attach again.

Ankur

[rodney.adams]

sorry about that. here ya go......

[Kevin Dorrell]

It's your static routes that are wrong. Each router is routing the traffic back to its own Ethernet instead of to the serial line.

On R1 you need ip route 172.16.3.0 255.255.255.0 Serial0/0, and on R2 you need ip route 172.16.4.0 255.255.255.128 Serial0.

Kevin Dorrell

Luxembourg

[ankurbhasin]

Hi Rodney,

Thats very right remember when you configure static route you have 2 options

1) to give next hop

ip route

2) to give exit interface

ip route

Option to give exit interface is good because its administrative distance will always be 0 and option for next hop will have administrative distance of 1 so exit interface will be more prefereable route.

But for a small network like yours both the option play a same role. So just change the exit interface to serial 0 and everything will be ok.

HTH

Ankur

[Kevin Dorrell]

Ankur,

Sorry to be pedandtic, but .. you are right that the static to an interface is somehow preferred, but the administrative distance is still 1. Try doing a detailed show ip route a.b.c.d for a specific network in your routing table that is routed to an interface, and you will see what I mean.

Kevin Dorrell

Luxembourg

[ankurbhasin]

Hi Kevin,

This is what I used to think earlier but when I was studying for CCNP BCRAN book by Brian Morgan, Craig Dennis I found this stuff there and there should be some reason why static routes with exit interface have more priority then statis routes with next hop ip address.

http://www.netcordia.com/tools/tools/books/advip-first-edition/drafts1/ch3.html

Please correct me if I am wrong.

Ankur

[Kevin Dorrell]

Ankur,

There is quite a lot of literature that says that an interface static has an AD of 0, including some of the older editions of CCNA and CCNP study guides. But when I checked through the latest editions at Networkers, I found that this "fact" had been removed from most of them.

Here is a pointer to a conversation I had in December about this topic:

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40.1dd6dc54/22#selected_message

If you do a show ip route on such a static, you get this on a 2509 IOS 12.1(1):

TS0#conf t

Enter configuration commands, one per line. End with CNTL/Z.

TS0(config)#ip route 192.168.41.128 255.255.255.252 Ethernet 0

TS0(config)#^Z

TS0#show ip route 192.168.41.129

Routing entry for 192.168.41.128/30

Known via "static", distance 1, metric 0 (connected)

Routing Descriptor Blocks:

* directly connected, via Ethernet0

Route metric is 0, traffic share count is 1

You are right that there is some mechanism that causes interfaces statics to take priority over IP statics, but I don't know exactly what it is. But it doesn't seem to be Administrative Distance.

Could it be perhaps there is a hierarchy based on the number of indirections you have to go through to identify the exit interface, or something like that?

I find it very confusing - six of one and half-a-dozen of the other.

Kevin Dorrell

Luxembourg

[devsharma]

Rodney,

Your static route has an issue,change the exit interface to S0 and S0/0 respectively and you shud be fine.

Dev

[rodney.adams]

Sorry to just getb back on this topic. I changed the exit interfaces like everyone agreed. Still no luck.

[Edison Ortiz]

Are you testing connectivity from the router or from a PC behind the router ? If PC behind router, what's the default gateway and IP on that PC ? If from router, are you able to ping both the serial and ethernet interface at the other end ? It could be a layer 2 issue here . Can you post SH IP ROUTE from each router as well as SH IP INT BRIEF ?

[rodney.adams]

I have the outputs from each router and also a crude diagram of my network. here are the outputs: