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Webcast-Catalyst9k
New Member

Eigrp can not establish neighbor between L3 switch and C4700...

Hi... I have a question...

I have a router cisco4700 has a FastEthernet and a 6-port Ethernet.

Two L3 3550 switchs are connected to it. One is connected to FastEthernet, and another is Ethernet.

Router 4700 can find one of the switchs via FastEthernet but not via Ethernet.

So I issued the command 'show ip eigrp neighbor' and the result is below.

You can verify one of RTOs is very high and Uptime is very short... It seems 3550 can not establish neighbor with router via Ethernet...

Router's FastEthernet is connected Fa0/45 and Ethernet is connectd Fa0/46.

I wonder why they can not establish neighbor each other only via ethernet.

------------------------------------------------------------------------------------------------------

3550b#sh ip eigrp nei

IP-EIGRP neighbors for process 19

H Address Interface Hold Uptime SRTT RTO Q Seq Type

(sec) (ms) Cnt Num

0 172.30.252.5 Fa0/46 12 00:01:02 1 5000 7 0

6 172.30.20.2 Vl20 13 1w4d 1 200 0 11839

5 172.30.23.2 Vl23 13 1w4d 1 200 0 11842

4 172.30.24.2 Vl24 12 1w4d 1 200 0 11840

3 172.30.21.2 Vl21 14 1w4d 2 200 0 11843

1 172.30.22.2 Vl22 12 1w4d 1 200 0 11841

2 172.30.252.13 Fa0/45 10 19w6d 1 200 0 50658

------------------------------------------------------------------------------------------------

12 REPLIES
Gold

Re: Eigrp can not establish neighbor between L3 switch and C4700

Try pinging 224.0.0.10, and see if you get a response from the other router. If not, you're hitting a multicast problem between the two. If that works, then make certain you can unicast ping between the two. Finally, if both of those work, then try pinging with a range of sizes, to make certain that full mtu packets are making it across the link.

If all of these work, then we'll need more information for this one.

Russ

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

Thank you for your reply...

I tried pinging 224.0.0.10... and I've never seen any response from the neighbor via ethernet as you said also unicast couldn't get response too.

As I said, this router is attatched with L3 switch(3550)...

Is there any bug in router's IOS 11.2(12)P or L3 switch's software?

L3 switch has System image file is "flash:c3550-i5q3l2-mz.121-11.EA1/c3550-i5q3l2-mz.121-11.EA1.bin"

If not, how can I try solving this problem?

Gold

Re: Eigrp can not establish neighbor between L3 switch and C4700

I would guess the problem isn't a bug--but it is a layer 2 connectivity issue. I'd first check the vlans the two routers are in, to make certain they are in the same broadcast domain, and then check the switch's cam table to make certain it sees all of the mac addresses on the right ports for these two.

I can't imagine there's a problem communicating between the two different types of media that is this radical, but I'm really a routing geek, not a switch geek, so....

:-)

Russ

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

Hi Russ..

I really thank you for your reply...

I check the switch's cam table and there is no table for the router, because the port is no more 'switch port access mode'.

So I think any information for the router is in the arp table.

There is a message like this

------------------------------------------------------------------------

Internet 172.30.252.5 0 Incomplete ARPA

------------------------------------------------------------------------

172.30.252.5 is the router's Ethernet IP. I think this switch can not map the mac and IP. Here, How do the switch get the IP of the router?

This is my first question.

And Router doesn't have any information about the switch via this Ethernet.

below is result of 'show int e0'

-------------------------------------------------------------------------

Ethernet0 is up, line protocol is up

Hardware is Am79c970, address is 00e0.b02b.eada (bia 00e0.b02b.eada)

Internet address is 172.30.252.5/30

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load 1/255

Encapsulation ARPA, loopback not set, keepalive set (10 sec)

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:05:33, output 00:00:00, output hang never

Last clearing of "show interface" counters 20w1d

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

0 input packets with dribble condition detected

4079298 packets output, 331786470 bytes, 0 underruns

4 output errors, 0 collisions, 4 interface resets

0 babbles, 0 late collision, 0 deferred

4 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

---------------------------------------------------------------------------------------------------

There is just output and no more input... It means L3 switch have not sent any packet, right? Or router's ethernet is fault... is it possible?

I think this is why they can not make eigrp neighbor each other.

Do you need any other information?

^.^

Jake

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

You answered my another question... right?

Anyway thank you very much....

^^

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

It might be a duplex issue or cable issue. That stuff always gets me......Never know : )

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

I tried to change the duplex and speed.

From 10/half to auto/auto and auto/auto to 10/half...

But there is no change...

As you've seen what I wrote, the router has only output count(no input) and the switch has only input count(no output)...

And the switch's output buffer failures count is growing...

Indeed, the switch can not give any packet to router but router can give.

It can be happened when the cable has problem?

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

Hi,

Are you able to see the switch as router's CDP neighbor, please issue the command "show cdp neighbor " for L2 layer connectivity.

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

Not sure if you tried this when you changed the switch port settings...

Confirm you have a link light on the switch port you are connecting to

Set the switch port to speed to 10 mb

set the switch port to half duplex

on the router shut and then no shut the ethernet interface

if you did not bounce the router interface, you may not have been able to clear that connection.

HTH

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

Hi

As I wrote, the Router can send any packet to the switch but the switch can not.

The switch just recieve from router, so CDP neighber can verify on the switch.

But not in the router because router can not recieve any packet from the switch.

And I tried to shut and no shut. The symptom can not change.

Jake^^

Re: Eigrp can not establish neighbor between L3 switch and C4700

Try swapping the connection from router to the second 3550 switch and see if you still see this problem...

New Member

Re: Eigrp can not establish neighbor between L3 switch and C4700

Hi

Can you check the media and depending on the media-type use the media-type command under the interface. Because I think by default it is AUI.

If the media type is AUI, also try to check the SQE.

Thanks

Agnelo Dcunha

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