From: Bob Sinclair (bsin@cox.net)
Date: Sat May 21 2005 - 08:05:01 GMT-3
Simon,
Have you tried switchport nonegotiate on the the port facing Rtr 6? Without
it we often see inconsistency when connecting to bridged router interfraces.
Also, the fact that the Cost to Rtr 6 is 19 suggests it is a 10 Mbps port. Do
Cisco 10 Mbps ports support ISL?
Bob Sinclair
CCIE #10427, CCSI 30427, CISSP
www.netmasterclass.net
----- Original Message -----
From: simon hart
To: simon hart ; ccielab@groupstudy.com
Sent: Saturday, May 21, 2005 6:30 AM
Subject: RE: Bridging on isl trunks
Further to the scenario below, it appears that I can get this scenario to
work if I change the trunking encapsulation to Dot1q. However it will not
function as ISL. Any pointers much appreciated
Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
simon
hart
Sent: 21 May 2005 08:39
To: ccielab@groupstudy.com
Subject: Bridging on isl trunks
Hi all,
I am having a problem bridging across two isl trunks on a router. My set
up
is like this
13.13.23.1 13.13.23.5
Rtr 1 Rtr 5
| |
vlan 4 vlan 1
\ /
\ /
\ /
\ /
Switch 1
|
|
isl trunk
fa0/0.1 fa0/0.4
vl1 vl4
Rtr6
I am attempting to have Rtr 1 speak to Rtr 5 by bridging on Rtr6. At first
sight I would see this as pretty straightforward, however I a cannot seem
to
get it working.
My config on Rtr 6 looks like this
bridge irb
bridge 1 protocol ieee
int fa1/0.1
encaps isl 1
bridge 1
int fa1/0.4
encaps isl 4
bridge 1
My mac table for Bridge 1 on Rtr 6 looks like this
Rack1R6#sh bridge 1
Total of 300 station blocks, 297 free
Codes: P - permanent, S - self
Bridge Group 1:
Address Action Interface Age RX count TX count
0000.0c0a.2804 forward Fa1/0.4 1 1 0
Rtr 1
0003.6b37.c981 forward Fa1/0.1 0 4 0
Rtr 5
000e.381f.d106 forward Fa1/0.1 0 35 0
Int Vlan 1
I can confirm that the mac addresses for each are those that I would expect
from Rtr 1, Rtr 5 and my Interface Vlan 1 on Switch 1.
Now I cannot ping between the two, I get no response. It appears that the
Routers (either 1 or 5) send out an ARP but gets no reply. On each arp the
RX count increases by one on Rtr6, but the Tx Count does not go up. This
leads me to believe that bridge 1 on Rtr 6 is not forwarding the frames
recieved on one vlan to the other
SPANNING TREE
I have noticed that there maybe some inconsisitency with spanning tree.
Here
is the output of SPT on Rtr 6 ( I attempted to make R6 the root by using
bridge priority 0)
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 0
Address 0005.9bc5.fad0
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 0
Address 0005.9bc5.fad0
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port
ID
-------------------- ------- ---- ----- --- ----- --------------------
-----
--
FastEthernet1/0.1 128.17 128 19 FWD 0 0 0005.9bc5.fad0
128.17
FastEthernet1/0.4 128.18 128 19 FWD 0 0 0005.9bc5.fad0
128.18
Here is the output from Switch 1 for both Vlan 4 and Vlan 1
VLAN0004
Spanning tree enabled protocol ieee
Root ID Priority 32772
Address 000e.381f.d100
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32772 (priority 32768 sys-id-ext 4)
Address 000e.381f.d100
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Port ID Designated Port
ID
Name Prio.Nbr Cost Sts Cost Bridge ID
Prio.Nbr
---------------- -------- --------- --- --------- --------------------
-----
---
Fa0/1 128.1 100 FWD 0 32772 000e.381f.d100
128.1
Fa0/6 128.6 19 FWD 0 32772 000e.381f.d100
128.6
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 000e.381f.d100
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000e.381f.d100
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 15
Interface Port ID Designated Port
ID
Name Prio.Nbr Cost Sts Cost Bridge ID
Prio.Nbr
---------------- -------- --------- --- --------- --------------------
-----
---
Fa0/5 128.5 100 FWD 0 32769 000e.381f.d100
128.5
Fa0/6 128.6 19 FWD 0 32769 000e.381f.d100
128.6
So it seems that both the switch and Rtr 6 think they are the roots for
both
spanning trees!!
Does anyone have any idea why this should be occurring, or any other
useful
debug tools that I could use to determine the underlying cause of this
problem.
TIA
Simon
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