dot1q compatibility between Linksys and Cisco switches

[oddyager]

I'm trying to connect my Linksys SRW2008 to a Cisco 6500 to take full advantage of the gigabit network. Treating this like any other Cisco switch connecting to the 6500, I configured the port on the 6500 as this:

switchport
switchport trunk allowed vlan 1-4,8,10,12,15-4094
switchport mode trunk
no ip address
speed 1000
duplex full
udld port
spanning-tree guard none

and on the Linksys side I configured the port to be Full 1000 and in trunk mode (leaving other settings on default). When I plug it in, I'm getting no connectivity and no lights. Has anyone connected a switch like this up to a Cisco switch? Maybe I am approaching this the wrong way?

Any help is appreciated.

 

[jlazzaro]

regardless of the trunking, you should be getting link lights. have you tried auto instead of a hard-coded speed on both sides? both sides are not shutdown? try removing udld on the 6500?

 

[oddyager]

Right, it works fine if normal access mode. It's just when I try to trunk. Both sides are not shutdown and I set both speeds to auto. Same. No connectivity. I tried changing cables but that doesn't seem to be the issue.

 

[spidey07]

post "show int trunk" on the 6500. Also look at the logs.

There should be no problems trunking these two.

Another thing to check is flow control on both sides. Making it a trunk "could" have changed the flow control on the linksys. If this doesn't match, you will get no link. also force the trunk mode to ON and encap 802.1q.

 

[oddyager]

GigabitEthernet1/33 is down, line protocol is down (notconnect)
Hardware is C6k 1000Mb 802.3, address is 0012.437f.4564 (bia 0012.437f.4564)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 0/255, rxload 0/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, Auto-speed
input flow-control is off, output flow-control is off
Clock mode is auto
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:12:42, output hang never
Last clearing of "show interface" counters 12w6d
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
5 packets input, 192 bytes, 0 no buffer
Received 5 broadcasts (3 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
283 packets output, 15409 bytes, 0 underruns
0 output errors, 0 collisions, 3 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out



Maybe its just the way I'm connecting it? The Linksys is connected to a patch panel via ethernet cable. The patch panel is connected to the home run via crossover. The home run is connected to the 6500 via ethernet cable.

 

[spidey07]

get rid of the crossover cable. 1000 Base-T has an auto-mdi feature and you shouldn't use crossover cables.

Other than that look into flow control settings on both sides as this will surely not get a link if there is a mismatch.

 

[oddyager]

I replaced the crossover with regular ethernet and checked flow-control settings on both sides (both turned off). No luck and no lights.

 

[jlazzaro]

if cabling was really an issue, access mode wouldnt work either. your 6500 side looks good from what i can see...leaning towards the linksys. Do you have a cisco switch you can swap with the linksys to verify the trunk configuration?

 

[spidey07]

So you DO get link when it's a non trunk port?

If so that would eliminate cabling.

I need to see interface configurations from both sides. Also "show int trunk g5/2" or whatever 6500 port. I didn't see where you set the encapsulation to dot1q originally. If the trunk mode is desirable I can see it not coming up as that is a cisco only setting. Needs to be "ON" "dot1q" "allow all".

Also check native vlan on both sides, although if it were a native mismatch you should get link, just the switch barking about native vlan mismatch.

 

[jlazzaro]

i dont think you can set the trunk encap on the 6500. since cisco phased out isl, dot1q is the new default. at least thats what im seeing on my 4500...

 

[spidey07]

Originally posted by: jlazzaro
i dont think you can set the trunk encap on the 6500. since cisco phased out isl, dot1q is the new default. at least thats what im seeing on my 4500...

of course you can. But that's what the OP is missing. He isn't setting the encapsulation and it's probably set to negotiate. He needs to force both the trunk mode (on, desirable, auto) and the encapsulation (dot1q, isl, negotiate).

so his config should...

switch trunk encap dot1q
switch mode trunk
switch trunk allowed vlan all

that will make trunk mode on, encap dot1q no negotiate, native vlan 1, allow all vlans. it could be DTP protocol causing him problems.

This is where the "show int trunk" command is so valuable, he needs to see how the trunk is setup.

also more thoughts...make sure the vlans on each switch are indeed up and active.

 

[oddyager]

Hmm, I don't have the option to configure encapsulatuon dot1q on the 6500. When I do switchport trunk ? There isn't a command there. Trunk mode is on for the Linksys and there are also no additional options I can see to allow further changes. And vlan on each are up and active.

Here is a screenshot of the Linksys config:

http://pics.bbzzdd.com/users/oddyager/linksys.GIF
http://pics.bbzzdd.com/users/oddyager/linksys2.GIF

 

[spidey07]

Something is wrong with that 6500.

LAB6509(config)#int g7/1
LAB6509(config-if)#switch trunk ?
allowed Set allowed VLAN characteristics when interface is in trunking mode
encapsulation Set trunking encapsulation when interface is in trunking mode
native Set trunking native characteristics when interface is in trunking mode
pruning Set pruning VLAN characteristics when interface is in trunking mode

LAB6509(config-if)#switch trunk encap ?
dot1q Interface uses only 802.1q trunking encapsulation when trunking
isl Interface uses only ISL trunking encapsulation when trunking
negotiate Device will negotiate trunking encapsulation with peer on interface

LAB6509(config-if)#switch trunk encap

But still, do a "show int trunk <interface>"

 

[oddyager]

6500catsw#show int trunk ?
module Limit display to interfaces on module
| Output modifiers
<cr>


No option to go into just one interface. Doing "show int trunk" gives me all and there is no info on 1/33 (which is where I have it configured) and I'm assuming since there is no connectivity thats why the info isnt showing? I do have other cat switches hooked up to here.

You also mentioned that since Linksys doesn't have dot1q then how else can I do this? I want to avoid plugging this onto the 3560 I have since its only going to be full 100 and ideally this should be able to connect to the 6500 having one port from the Linksys be the uplink and have full gigabit running this path and the other ports can be whatever.

 

[spidey07]

whoah, you must be running some seriously old code or the original sup1. those things sucked.

can I get a "show ver"?

-edit- doh, I forgot...to limit it to an interface "show int g7/1 trunk"

 

[jlazzaro]

Originally posted by: spidey07

Originally posted by: jlazzaro
i dont think you can set the trunk encap on the 6500. since cisco phased out isl, dot1q is the new default. at least thats what im seeing on my 4500...

of course you can. But that's what the OP is missing. He isn't setting the encapsulation and it's probably set to negotiate. He needs to force both the trunk mode (on, desirable, auto) and the encapsulation (dot1q, isl, negotiate).

so his config should...

switch trunk encap dot1q
switch mode trunk
switch trunk allowed vlan all

that will make trunk mode on, encap dot1q no negotiate, native vlan 1, allow all vlans. it could be DTP protocol causing him problems.

This is where the "show int trunk" command is so valuable, he needs to see how the trunk is setup.

also more thoughts...make sure the vlans on each switch are indeed up and active.

NAB4510R(config)#int gig5/10
NAB4510R(config-if)#switch trunk ?
allowed Set allowed VLAN characteristics when interface is in trunking mode
native Set trunking native characteristics when interface is in trunking mode
pruning Set pruning VLAN characteristics when interface is in trunking mode

NAB4510R#sho int trunk

Port Mode Encapsulation Status Native vlan
Po3 on 802.1q trunking 1
Po4 on 802.1q trunking 1
Po5 on 802.1q trunking 1

running 12.2(25)EWA5.

 

[spidey07]

jzarro,

your supervisor may not support ISL trunking, hence it will only do dot1q

-edit- you can always do a "show int capabilities" to see what an interface can do.

 

[nightowl]

I am not sure where you are on this but you may want to try "switchport nonegiotiate". This turns off DTP which I have seen cause problems with interoperability with non-Cisco switches. Also, as Spidey said that you may be running into an instance where dot1q is not supported. This however, would be a function of the linecard and not the supervisor. So, if you could post the model of the linecard that you are connecting to that would be helpful as well. The supervisor should support dot1q since you are running IOS and it appears that you have a Sup720 or a Sup32 since there is not a SUP in slot 1. So you are good there.

Edit: One more thing that I thought of, did you set a native VLAN on both switches?

 

[spidey07]

Originally posted by: nightowl
I am not sure where you are on this but you may want to try "switchport nonegiotiate". This turns off DTP which I have seen cause problems with interoperability with non-Cisco switches. Also, as Spidey said that you may be running into an instance where dot1q is not supported. This however, would be a function of the linecard and not the supervisor. So, if you could post the model of the linecard that you are connecting to that would be helpful as well. The supervisor should support dot1q since you are running IOS and it appears that you have a Sup720 or a Sup32 since there is not a SUP in slot 1. So you are good there.

Edit: One more thing that I thought of, did you set a native VLAN on both switches?

agreed...there isn't anything that should prevent this from working properly. 802.1q is a laer2 thing, having a hard time understanding how you wouldn't get L1 link. Logs and show commands should tell us why.