arp table is incomplete

[mnieuwendijk]

Hi

I got an problem with an connection between an 4500 router and several 2950 catalyst switches.

When i give the command: "sh arp" on my router, there are ip addresse with an incomplete mac address.

And it is impossible to connect to the switch outside his ip range.

It is not with all of my switches but random.

How is this possible.

Al the software versions on the switches are the same.

Link's between the switches and the router are good no errors.

Help is needed becouse i have to solve this on monday.

thanks.

Marc

[Kevin Dorrell]

If the ARP cache entry says "(incomplete)", that is usually nothing to worry about. All it means is that the router has broadcast an ARP request, and has not received any reply yet. However, if you bear that fact in mind, it might give you some ideas about your other problems.

Also, it is quite normal not to be able to connect to the switch outside its own (sub-)network. To do that, you would need to go through the router. The first thing to do is to make sure that the switch has a default gateway configured that is the address of the router in the management (sub)network of the switch.

Perhaps if you post the configs of your router and switches, we could have a closer look at them.

Kevin Dorrell

Luxembourg

[mnieuwendijk]

ok a bit further background info.

I replaced an 2926 catalyst switch for an 3550 catalyst switch. (the first switch connected to the router)

On that switch the vlan's are configured, he is also the vtp server.

On the 2926 switch the vlan were configured before.

Before the change everyting worked fine.

Nothing is changed at the config of the switches.

Du to closure of the location i could not perform an rolback, I can remote cofigure the switches, so any solution would be fine.

I shall send the configurations later this day.

Marc

[frennzy]

VTP advertisements will only be sent across trunks. Did you properly configure the interswitch links as trunks? (This is my bet...especially if the other switches have not been powered off...you would not notice that something isn't working properly, since they will still have their copy of the VLAN database)

Are all the other switches in client mode? If so, you have introduced a new server with no information, and it may have updated the clients with what it knows...namely...nothing. I would expect this would do much more than just cause incomplete ARP entries...it would stop all communications.

[TerheunJ]

I believe the default trunk protocol on a 3550 is Dot1q

not isl. I don't know the abilities of the 2900 series, but if they are ISL then you will not communicate with the 3500. If you are setting up the 3550 as your VTP server, you will need to adjust the 29xx as CLIENTS. Personally I would flush the vlan database on the 29xx'z get your trunks working, and see if it workz..