Cisco VPLS (BGP) and MTU

tholbrook · Thu Jun 04, 2009 6:03 pm

Is there a way to set the MPLS MTU on dynamically created VPLS interfaces? Specifically in setting up a Cisco style VPLS using BGP.

Obviously when you statically create the interface you do in the "interface VPLS" statement but when you set a VPLS up using BGP there doesn't seem to be anywhere to set it:

[admin@A] > /interface vpls cisco-bgp-vpls set cisco-bgp-vpls1 ?
Change properties of one or several items.

<numbers> -- List of item numbers
bridge -- 
bridge-cost -- 
bridge-horizon -- 
comment -- Set comment for items
disabled -- 
export-route-targets -- 
import-route-targets -- 
l2router-id -- 
name -- Interface name
route-distinguisher -- 
vpls-id --

Thanks

Mplsguy · Thu Jun 04, 2009 9:56 pm

Currently there is no way to do that. Is there any particular reason why you need this feature?

tholbrook · Thu Jun 04, 2009 11:33 pm

In a generic case we might need it for all the normal reasons you need to be able to adjust protocol MTU. For example I may be running multiple labels and/or 802.1Q tags through a network where have a device like a switch that has a lower physical MTU than required and cannot fragment.

In this particular case though I have set up a simple 3 node BGP MPLS network of 493AHs and am unable to pass traffic larger than 1474 bytes (IP). I expect that they would just fragment the frames but they aren't. Setting the MPLS MTU was just my first attempt at troubleshooting. Any suggestions would be welcome.

tholbrook · Fri Jun 05, 2009 1:21 am

This should be easy to reproduce btw. The RBs are connected in a straight line:

/--e9-(A)-e2----------------e3-(B)-e2---------------e3-(C)-e9---/

The intent is to create a dynamic VPLS from one side to the other. Router B is a route reflector. As I mentioned the network comes up and operates fine. There is just an issue with the frame size that will successfully pass. Here are the non-default configurations settings:

/system identity set name=A
/interface bridge add name=lo0
/interface bridge add name=customer1
/ip address add interface=lo0 address=10.127.0.1 netmask=255.255.255.255
/ip address add interface=ether2 address=10.1.0.1 netmask=255.255.255.0
/routing ospf instance set default router-id=10.127.0.1
/routing ospf network add area=backbone disabled=no network=10.1.0.0/24
/routing ospf network add area=backbone disabled=no network=10.127.0.1/32
/routing bgp set default router-id=10.127.0.1
/routing bgp peer add remote-as=65530 update-source=lo0 instance=default remote-address=10.127.0.2 address-families=l2vpn-cisco
/mpls ldp set enabled=yes transport-address=10.127.0.1 lsr-id=10.127.0.1
/mpls ldp interface add interface=ether2
/interface vpls bgp-vpls add bridge=customer1 bridge-horizon=1 route-distinguisher=10:1 site-id=1 

/system identity set name=B
/interface bridge add name=lo0
/ip address add interface=lo0 address=10.127.0.2 netmask=255.255.255.255
/ip address add interface=ether3 address=10.1.0.2 netmask=255.255.255.0
/ip address add interface=ether2 address=10.2.0.1 netmask=255.255.255.0
/routing ospf instance set default router-id=10.127.0.2
/routing ospf network add area=backbone disabled=no network=10.1.0.0/24
/routing ospf network add area=backbone disabled=no network=10.2.0.0/24
/routing ospf network add area=backbone disabled=no network=10.127.0.2/32
/routing bgp set default router-id=10.127.0.2
/routing bgp peer add remote-as=65530 update-source=lo0 instance=default remote-address=10.127.0.1 address-families=l2vpn-cisco route-reflect=yes
/routing bgp peer add remote-as=65530 update-source=lo0 instance=default remote-address=10.127.0.3 address-families=l2vpn-cisco route-reflect=yes
/mpls ldp set enabled=yes transport-address=10.127.0.2 lsr-id=10.127.0.2
/mpls ldp interface add interface=ether2
/mpls ldp interface add interface=ether3

/system identity set name=C
/interface bridge add name=lo0
/interface bridge add name=customer1
/ip address add interface=lo0 address=10.127.0.3 netmask=255.255.255.255
/ip address add interface=ether3 address=10.2.0.2 netmask=255.255.255.0
/routing ospf instance set default router-id=10.127.0.3
/routing ospf network add area=backbone disabled=no network=10.2.0.0/24
/routing ospf network add area=backbone disabled=no network=10.127.0.3/32
/routing bgp set default router-id=10.127.0.3
/routing bgp peer add remote-as=65530 update-source=lo0 instance=default remote-address=10.127.0.2 address-families=l2vpn-cisco
/mpls ldp set enabled=yes transport-address=10.127.0.3 lsr-id=10.127.0.3
/mpls ldp interface add interface=ether3
/interface vpls bgp-vpls add bridge=customer1 bridge-horizon=1 route-distinguisher=10:1 site-id=2

Mplsguy · Fri Jun 05, 2009 9:56 am

What exact version and packages are you using? Which routerboards and which ports are used in your setup? What is mpls-mtu setup on all routers?

When you use BGP AF l2vpn-cisco, BGP distributes NLRIs created by /interface cisco-bgp-vpls, when you use BGP AF l2vpn, BGP distributes NLRIs created by /interface bgp-vpls.

tholbrook · Mon Jun 08, 2009 7:00 pm

I posted the wrong config above. The working configuration has the correct "/interface vpls cisco-bgp-vpls" statements. As I mentioned though there isn't a problem with its basic functionality, only the large frames.

Here are the other details:

-These are 3 identical 493AH boards with the following software:

[admin@A] > system routerboard print
       routerboard: yes
             model: "493AH"
     serial-number: "1A8E01EECE87"
  current-firmware: "2.18"
  upgrade-firmware: "2.20"
[admin@A] /system package> print
Flags: X - disabled 
 #   NAME                    VERSION                    SCHEDULED              
 0   system                  3.24                                              
 1   routerboard             3.24                                              
 2 X ipv6                    3.24                                              
 3   mpls-test               3.24                                              
 4   dhcp                    3.24                                              
 5   routing-test            3.24                                              
 6 X routing                 3.24                                              
 7   hotspot                 3.24                                              
 8   wireless                3.24                                              
 9   routeros-mipsbe         3.24                                              
10   security                3.24                                              
11   ppp                     3.24                                              
12   advanced-tools          3.24

-The ports are reflected in my line diagram above. I'll redraw it here:

/--e9-(A)-e2----------------e3-(B)-e2---------------e3-(C)-e9---/

-I have not changed any mtu settings so they are all at defaults:

/mpls interface
add comment="" disabled=no interface=all mpls-mtu=1508

Cisco VPLS (BGP) and MTU

Cisco VPLS (BGP) and MTU

Re: Cisco VPLS (BGP) and MTU

Re: Cisco VPLS (BGP) and MTU

Re: Cisco VPLS (BGP) and MTU

Re: Cisco VPLS (BGP) and MTU

Re: Cisco VPLS (BGP) and MTU

Who is online