BGP - trunk not working

[t.oconnor]

Hi,

Telco provided a BGP connection on MPLS network. When I connect router directly to Telco switch I can see BGP neighbor, so my router BGP config is OK. However, I need to put this router in a diffferent building and want to bring the connection over on a "trunk"; now I loose the BGP neighbor. I'm sure I did this before and it worked OK. I'm trunking between 2 x2950 switches using this config on each switch

!

interface FastEthernet0/41

switchport trunk allowed vlan 855

switchport mode trunk

duplex full

speed 100

end

!

I also configured the trunk as vlan 1214, which is the encapsulation provided by the Telco (dot1Q 1214). Any ideas what is wrong here?

[Jon Marshall]

Firstly if you are only allowing one vlan on the trunk then why does it have to be a trunk link ?

The telco connection, are you saying it is an 802.1q connection to you ie. they send tagged traffic to you on a trunk or is it simply a routed connection ?

Jon

[t.oconnor]

Hi,

This is the config provided from telco for my BGP interface on the router.

interface GigabitEthernet0/1.1214

description GigabitEthernet0/1.1214 dot1q vlan id=1214

encapsulation dot1Q 1214

ip address 46.43.24.250 255.255.255.252

no shutdown

Regards,

Terry O'Connor

From:

"jon.marshall"

To:

Terry O'Connor1/Ireland/IBM@IBMIE

Date:

07/10/2011 12:03

Subject:

- Re: BGP - trunk not working

Cisco Support Community

Re: BGP - trunk not working

created by jon.marshall in WAN, Routing and Switching - View the full

discussion

Firstly if you are only allowing one vlan on the trunk then why does it

have to be a trunk link ?

The telco connection, are you saying it is an 802.1q connection to you ie.

they send tagged traffic to you on a trunk or is it simply a routed

connection ?

Jon

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[Jon Marshall]

Terry

Okay then you need to have that vlan allowed on the trunk and you would need to configure that vlan in your vlan database on both your 2960 switches.

Actually you only really need the first switch, the one the telco connects to, to be a trunk link. The link between the 2 switches could be a simple access port in vlan 1214 as you only seem to need one vlan on that link. If you need multiple vlans then yes make it a trunk.

Note also that your switches will need to be in VTP transparent mode because vlan 1214 is an extended vlan range number and you can't add this to the vlan database in VTP server/client mode.

Have you already tried this setup ?

Jon

[John Blakley]

I agree with Jon. You'll only need an access port. Are you connecting your switches directly to the ISPs switch? What's your point of connection to the ISPs switch if you're connecting to the 2950s now?

[t.oconnor]

Hi,

Telco is 3560 - port 21; I have x-over to 2950-A port 41 configured as

switchport mode trunk allowed vlan 1214; link is up;

GigFibre to 2950-B, gig interfaces trunk all VLANs; fibre interfaces up

(other vlans trunked over the fibre are OK)

2950- port f0/41 configured as switchport mode access vlan 1214; interface

is up, connected to router f0/0 ;

I have tried both 2950 ports as trunks (allowed 1214 only) and also both

as access vlan 1214; now a trunk on the f0/41 connecting to Telco and

access vlan 1214 on the 2nd 2950. Still no joy.

!

!

interface FastEthernet0/0

no ip address

speed 100

full-duplex

!

interface FastEthernet0/0.1214

encapsulation dot1Q 1214

ip address 46.43.x.x 255.255.255.252

!

Regards,

Terry

From:

"j.blakley"

To:

Terry O'Connor1/Ireland/IBM@IBMIE

Date:

07/10/2011 12:22

Subject:

- Re: BGP - trunk not working

Cisco Support Community

Re: BGP - trunk not working

created by j.blakley in WAN, Routing and Switching - View the full

discussion

I agree with Jon. You'll only need an access port. Are you connecting your

switches directly to the ISPs switch? What's your point of connection to

the ISPs switch if you're connecting to the 2950s now?

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Start a new discussion in WAN, Routing and Switching at Cisco Support

Community

[Jon Marshall]

Terry

interface FastEthernet0/0

no ip address

speed 100

full-duplex

!

interface FastEthernet0/0.1214

encapsulation dot1Q 1214

ip address 46.43.x.x 255.255.255.252

!

is the above from your router ? If so then you cannot configure an 802.1q subinterface because the switchport it is connected to is not a trunk. Change your config on the router to -

int fa0/0

ip address 46.43.x.x 255.255.255.252

speed 100

duplex full

and remove the fa0/0.1214 subinterface.

Jon