Thanks for everyone the response. This scenario was seen in production network.
Switch A is managed by us, Switch B is managed by client. We don't have visibility of switch B and the client has very little knownlodge of their own gears. Switch B is HP 2524, according to cdp discovery. Switch A is running ISL trunking connected with an external router. When I did "show cdp neig", i could see switch A list itself as its own neighbors on those two ports. Thus I guessed HP2524 must configured the same vlan for those two adjacent ports. Switch A spt would be PVST, switch B is MST. They should be able to communicate via access link, according to the theory, and that was what i saw. Saw messages like this: (fe0/7 is on vlan 7, fe0/8 is on vlan 8) %RTD-1-ADDR_FLAP: FastEthernet0/7 relearning 1087 addrs per min %RTD-1-ADDR_FLAP: FastEthernet0/7 relearning 1065 addrs per min %RTD-1-ADDR_FLAP: FastEthernet0/8 relearning 5 addrs per min %RTD-1-ADDR_FLAP: FastEthernet0/8 relearning 9 addrs per min Now from your lab result and what I saw, * if SW A and SW B are both running PVST, two switch won't communicate * if SW A and SW B are running different spanning tree types, two switches can communicate but the function of spanning tree doesn't work well. Paul > CL: where are you seeing a look? I have configured two switches based on > what I read below. sho spanning-tree gives me the following: > > Interface Port ID Designated Port > ID > Name Prio.Nbr Cost Sts Cost Bridge ID > Prio.Nbr > ---------------- -------- --------- --- --------- -------------------- ----- > --- > Fa0/1 128.1 100 FWD 0 4097 0009.b775.d400 128.1 > Fa0/7 128.7 100 FWD 0 4097 0009.b775.d400 128.7 > > meaning that port Fa0/22 and Fa0/24 are not recognizing vlan 1 at all. > > the switches both complain that there are vlan mismatches. > > 6d10h: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on > FastEther > net0/46 (1), with Switch_24 FastEthernet0/22 (7). > 6d10h: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on > FastEther > net0/48 (1), with Switch_24 FastEthernet0/24 (8). > 6d > > > >> -------------------- >> |switch A | >> --------------------- >> |(vlan 7) | (vlan 8) >> | | >> | | >> |(vlan 1) |(vlan 1) >> ------------------- >> | switch B | >> -------------------- >> | | | >> vlan 1 hosts >> >> >>In short, switch A has two ports configured with vlan 7, vlan 8 >>respectively. Swtich B all ports are at default vlan 1. >>links between swA and swB are access mode. >> >>This scenario creates bridging loop. But just can't figure out why STP >>fails to stop loop. > > > CL: again, I am not seeing a loop. I am seeing a problem and no way to fix > it other than to correct the vlan mismatch. > > CL: you sure you don't have another trunk configured on another port? > > > > >>Thanks in advance. >> >>Paul Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=58177&t=58099 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
