hugh discards in trunk port

[shihlin]

Hi, I have question about In-Discard in Catalyst 6509. I have a 802.1q turn setup between two switches (Catalyst 6509 and Catalyst 3550) the layout shows bellows:
Cat6509 ------ Point to Point Laser ========= Point to Point Laser ----- Cat3550

Now I been receiving In-Discard in Catalyst 6509 when I do show port mac # The Discard is about 8K / hours.

Cisco6509>> (enable) sh port mac 4/43
Port Rcv-Unicast Rcv-Multicast Rcv-Broadcast
-------- -------------------- -------------------- --------------------
4/43 75291 9229 2032

Port Xmit-Unicast Xmit-Multicast Xmit-Broadcast
-------- -------------------- -------------------- --------------------
4/43 79424 18210 26991

Port Rcv-Octet Xmit-Octet
-------- -------------------- --------------------
4/43 11546005 20790325

MAC Dely-Exced MTU-Exced In-Discard Out-Discard
-------- ---------- ---------- ---------- -----------
4/43 0 - 8554 0

Port Last-Time-Cleared
----- --------------------------
4/43 Wed May 25 2005, 12:42:51
Cisco6509>> (enable)


However when I check the Cat3550 it does not had any Out-Discard or error in show interface. I change the port in Catalyst 6509 but I still receiving the In-Discard in the new port. I thinking it maybe the Laser is acting up such as quality of links or line of sigh. Any suggestion regards to this issues is greatly appreciated thanks in advanced.

SL

 

[vipergg]

Make sure the vlans allow on the trunk are the same on both sides of the trunk, I think if they are different and the router see's a packet that isn't allow it will just disgard the packet . Just allow what is actually needed and don't allow all vlans across the link .

 

[shihlin]

Thanks vipergg,

It works, I pruning some extra vlan in cat3550 and the in-discard is decreased. However, I still reciving In-Discard in cat6500 like 70 / minutes

Thanks again,

SL


Catalsyt 6500:
Cisco6509>> (enable) sh port trunk
* - indicates vtp domain mismatch
# - indicates dot1q-all-tagged enabled on the port
Port Mode Encapsulation Status Native vlan
-------- ----------- ------------- ------------ -----------
4/43 on dot1q trunking 1
......
Port Vlans allowed and active in management domain
-------- ---------------------------------------------------------------------
4/43 1,5-6,100-102

Port Vlans in spanning tree forwarding state and not pruned
-------- ---------------------------------------------------------------------
4/43 1,5-6,100-102

************

Catalyst 3550:
cat3550#sh interfaces fastEthernet 0/47 trunk

Port Mode Encapsulation Status Native vlan
Fa0/47 on 802.1q trunking 1

Port Vlans allowed on trunk
Fa0/47 1,5-6,8-4094

Port Vlans allowed and active in management domain
Fa0/47 1,5-6,100-102,201

Port Vlans in spanning tree forwarding state and not pruned
Fa0/47 1,5-6,100-102
cat3550#