[nsp] IP-EIGRP: Neighbor A.B.C.D not on common subnet...

[Yuval Ben-Ari]

> -----Original Message-----
> From: Gert Doering [mailto:gert at greenie.muc.de] 
> Sent: Friday, January 31, 2003 7:16 PM
> To: Yuval Ben-Ari
> Cc: Thomas Renzy; cisco-nsp at puck.nether.net
> Subject: Re: [nsp] IP-EIGRP: Neighbor A.B.C.D not on common subnet...
> 
> 
> Hi,
> 
> On Wed, Jan 29, 2003 at 08:44:39AM +0200, Yuval Ben-Ari wrote:
> > I suspect the root for the problem is EIGRP hello packets being
> > multicast and the fact that the L2 switches (Catalyst XL 
> series in this
> > case) flood multicast frames on all ports including ports from other
> > Vlans. 
> 
> If they do that, it is a major bug.  Flooding MUST NOT spill over to
> other broadcast domains.  NEVER.

Well, it sure looks like this is what is happening, the port of the
router sending the hello's is explicitly configured on Vlan4:

interface FastEthernet0/33
 description XXX
 duplex full
 speed 100
 switchport access vlan 4
 spanning-tree portfast

while the port of the router complaining about the "Neighbor not on
common subnet" (on an adjacent switch connected by trunk) is left on the
Native VLAN (1):

interface FastEthernet0/9
 description XXX
 duplex full
 speed 100
 spanning-tree portfast

The trunk between the switches is a 4 port etherchannel with this config
(VLAN 4 is not even allowed):

interface FastEthernet0/45-48
 description TRUNK
 load-interval 30
 duplex full
 speed 100
 port group 2
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 1,400,1002-1005
 switchport mode trunk

Is anything wrong with the config or is it really Catalyst 3500XL flaw ?
 
> gert
> -- 
> Gert Doering
> Mobile communications ... right now writing from * Osnabrueck *
>