Dot1q on 2611 4

[JOAMON]

When I try enabling dot1q on a 2611 it will not communicate with the switch and/or anythig. Below is config. Used identical setup on 1841 and works great. Is there something special on a 2611 that needs to be anabled for this to work?

Switch
interface FastEthernet0/7
switchport mode trunk
switchport nonegotiate
speed 10
duplex full
mls qos trust cos
macro description cisco-router
spanning-tree portfast trunk
spanning-tree bpduguard enable

Router
interface ethernet0/1
no ip address
no ip route-cache
full-duplex
interface ethernet0/1.1
encapsulation dot1Q 1 native
ip address 192.168.26.28 255.255.255.0
no ip route-cache
no snmp trap link-status

IP of vlan 1 on switch is 192.168.26.34 255.255.255.0

 

[JOAMON]

I know what happend...thay caught a Virus from Linksys and instead of fixing the bugs.....it put them all back in.....

 

[JOAMON]

Maybe the fix was just put into the IP plus feature set....as this is and internal router and I no longer use it for Crypo I will loose tha advanced feature set and see if that helps as well.

 

[JOAMON]

Geez...I canst typed wary vell tinight

 

[jneiberger]

You might be right. At the time, I seem to recall that we were using IP PLUS.

 

[leedsit]

Hi,

Just labbed up with a 2612 connected to a 3560 Switch and had the exact same problem you had! Strange.... but got it working by performing the following.

On the 2612 Router

Int ethernet 0/0
ip address 192.168.1.1 255.255.255.0
int ethernet 0/0.2
ip address 192.168.2.1 255.255.255.0
int ethernet 0/0.3
ip address 192.168.3.1 255.255.255.0

On the switch

interface fastethent 0/1
switchport mode trunk
switchport nonegotiate
switch trunk encapsulation dot1q ( Native VLAN 1 as default )


vlan 1
ip address 192.168.1.2 255.255.255.0
vlan 2
ip address 192.168.2.2 255.255.255.0
vlan 3
ip address 192.168.3.2 255.255.255.0

That did the trick.

Because the NATIVE vlan carries untagged data, that is it does not carry the 4 extra bytes of Tagged information, it seems on the 26xx routers the physical interface I.E 0/0 accepts the untagged packets also as the Native vlan... then 0/0.2 0/0.3 0/0.4 accepts the associated tags for that vlan. I hoped that made sense.

So in essence on your switch, we beleive the native vlan to be .1 the second vlan .2 and the 3rd .3 and so on.... however on the router.... it appears the native is 0/0 then the second is 0/0.2 and the 3rd 0/0.3. This goes against most of the doco`s I can find... however just fully tested this and it works!!!! weird.







LEEroy
MCNE6,CCNA2,CWNA, Project+, CCSA

 

[jneiberger]

It's a bug. 802.1Q is not implemented correctly in these releases. For some reason, the router is expecting return traffic on the native VLAN to be tagged, so it discards untagged frames. You can see this if you turn on debugging, but I don't remember exactly which debugging I used when I first discovered this. I seem to remember that I used "debug ip arp" because I noticed that I wasn't getting any completed entries in my arp cache.

 

[directlyconnected]

switch trunk encapsulation dot1q I believe is the magic statement that makes it work. In CCNA class, I remember that our case study did not work until my lab partner pointed this out. The instructor argued that we did not need that statement, but without it ---nuth'n! I believe it was a 2611 router also. Cheerio.

Tim---CCNA, A+, Network+, tired, 2 kids, help me...

 

[jneiberger]

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