From: Chris Hugo (chrishugo@yahoo.com)
Date: Sat Sep 28 2002 - 17:23:37 GMT-3
Thanks Barry.
It seems like router with switch interactions is buggy period. This is bug #2 I came across in one week. If someone have a revision that does not have this issue. Please speak up.
thanks,
chris hugo
chris hugo
Barry Rowland wrote: Do a clear arp on both host 2 and the sw. Then ping from host 2 to the sw.
After you have done this, look at the arp table on host 2. You should see
the sw's mac
mapped to it's ip address.
Now look at the sw's arp table and if you have this "known" issue with the
3550
IOS, using irb, you will not see host 2's mac to ip mapping. However, if you
ping your default gateway and look at the sw's arp table you will see the
gateway's host
mac to ip mapping. Thus you can ping the gateway but not host 2.
This happened to me in the NMC1 class and we looked at it from several
different
config setups and always got the same results. If a host is on a different
vlan than
the sw's management int, then for some reason, when you ping the sw from the
host on a different vlan you will get a reply from the sw because you can
see this
in the remote host arp table, but the sw will not add an entry for the
remote host
that pinged it. All the while, you can ping anywhere in your network from
the sw.
And the irb interface can ping either the sw or the remote host in the other
vlan.
The instructors said that they are waiting on a reply from cisco on this
issue.
HTH
----- Original Message -----
From: "Chris Hugo"
To:
Sent: Friday, September 27, 2002 2:36 PM
Subject: Problem: Isolated VLANs with IRB 3550/2900
> Hi Folks,
>
> I have and interesting dilemma with my switch. Let me paint the picture.
>
> I have one switch. this switch has two vlans and one trunk. the trunk is
connected to a router that is running dot1q. Bridging is run between two out
of the three sub-interfaces.
>
> The two sub-int that is bridging belong to one bridge-group. I am running
IRB and ip is running on the IRB int.
>
> The other interface is running ip and not in the bridge group but in a
separate subnet.
>
> Their are two routers that are connected to the switch but are in
different vlans.
>
> The switch management vlan is also included in the router that is running
IRB. The default gateway on the switch that points to the IRB interface.
>
> #1 host that is in the same subnet but on a vlan other than the management
vlan of the switch.
>
> #2 host that is in a different subnet but on a vlan other than the
management vlan of the switch.
>
> The Problem:
>
> Switch can reach all interfaces on all hosts (routers) but not host #2.
>
> I believe the switch is not using the default gateway since host #2 ip add
is in the same subnet. And the fact that host #2 is in a different vlan will
isolate itself from the management vlan. The router can ping ALL interfaces
btw.
>
> ----------------------------------------------------------------------->
>
> How do we fix this problem? Did I miss something important in
Clark/Hamilton. I know it must be something. If you need me to paint more
pictures let me know.
>
> Please Help I Know It's Friday :)
>
> chris hugo
>
>
>
> ---------------------------------
> Do you Yahoo!?
> New DSL Internet Access from SBC & Yahoo!
---------------------------------
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