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Can't seem to get Vlan 1 (default) to trunk traffic through


I've been beating my head against this for a while since I've only
encountered this issue with our Extreme switches and none of our other brands.

For the life of me, I cannot get traffic to move through on the default vlan from our other switches.

I can trunk vlan 1 across on any other switch between them using the standard trunk mode (tagged), but on the Extremes (We have a Black Diamond X8 and numerous x670v, x670g2 and x770s) vlan 1 is blocked.

I've tried leaving the vlan in untagged mode on both sides, tagged mode, and every iteration inbetween.

I can see the default vlan grab an IP address from the DHCP server on that vlan, but it won't push the traffic through beyond that.

Is there some step I'm missing in getting the default vlan to work like any other 802.1q vlan?

7 replies

Userlevel 6
Hello Matthew,

Can you define "blocked"? Also, how are you testing the traffic flow through these switches?
Userlevel 7
- configure the port as tagged
# configure vlan "Default" add ports 1 tagged

- then you'd check whether you learn about other devices from the connected switch on the port
# show fdb vlan "Default"
I put a port untagged on the specific vlan in question and see if it A gets a DHCP address from the server and if I can pass traffic to the other equipment in said vlan.

The only vlan that is not passing any traffic is default. Away from the extremes I can get DHCP and pass traffic on vlan 1, on the extremes, every vlan BUT 1 works fine.

Each switch has a single port that acts as the trunk link carrying all the vlan traffic between the switches and each vlan is properly tagged on each side.

In cisco syntax, the basic config on an uplink would look like this:

int ethx/1/z
switchport mode trunk
switchport trunk allowed vlan 1-200,400-499
exit

in the case of the extremes we have

configure vlan 1-200,400-499 add port x:yy tagged

Only vlan 1 is not passing traffic on the extremes.
Userlevel 7
Matthew Rivard wrote:

I put a port untagged on the specific vlan in question and see if it A gets a DHCP address from the server and if I can pass traffic to the other equipment in said vlan.

The only vlan that is not passing any traffic is default. Away from the extremes I can get DHCP and pass traffic on vlan 1, on the extremes, every vlan BUT 1 works fine.

Each switch has a single port that acts as the trunk link carrying all the vlan traffic between the switches and each vlan is properly tagged on each side.

In cisco syntax, the basic config on an uplink would look like this:

int ethx/1/z
switchport mode trunk
switchport trunk allowed vlan 1-200,400-499
exit

in the case of the extremes we have

configure vlan 1-200,400-499 add port x:yy tagged

Only vlan 1 is not passing traffic on the extremes.

I'm a little rusty on my Cisco skills but have you set the native vlan - if not it's per default 1 and it's untagged.

That would mean you'd need to also set it untagged on the XOS.
Found the issue. Case of spanning tree being an arse.
Userlevel 6
Hello Matthew,

Whenever I hear "blocked" I wonder if it is STP. That's why I asked wondering if it was just a general term or if the switch was displaying the port as blocked. Glad you found it!
Yeah, removing the spanning-tree port type edge trunk (Trunk mode portfast) off the port and flapping the port removed the block I was seeing.

For me it was just a general term, no traffic was coming through, but nothing was showing up in the switch logs as to why.

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