ASR920 - user settable MTU on BDI interface not supported

[filopeter]

Hello,

I am trying to integrate ASR920 into an existing MPLS network, but I am not able to change the MTU on the BDI interface. My IGP is OSPF and I want to avoid the usage of the "ip ospf mtu-ignore" command in the interface settings... Any ideas how to solve this issue?

asr920-test(config)#interface bdi 2344

asr920-test(config-if)#mtu 1998

% Interface BDI2344 does not support user settable mtu.

Thanks,

Peter

[bhnegi · Accepted solution]

Hi Peter,

"MTU" configuration is not supported on BDI interface, it's a limitation. Only IP MTU  configuration is allowed on BDI interfaces. You can try "ip mtu 1998".

Best Regards,

Bheem

[Roberto Falconi]

I try with "ip mtu", but I got no results

the version IOS:

Cisco IOS XE Software, Version 03.15.01.S - Standard Support Release
Cisco IOS Software, ASR920 Software (PPC_LINUX_IOSD-UNIVERSALK9_NPE-M), Version 15.5(2)S1, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2015 by Cisco Systems, Inc.
Compiled Thu 25-Jun-15 03:15 by mcpre

[filopeter]

Hi Roberto,

if you change the ip mtu, you have to use the "show ip interface" command

On IOS platforms the ip mtu can be equal or less as mtu of physical interface, on IOS XE platforms you do not have this limit because the physical interface usually supports greater mtu than 1500B. 

P.

[Roberto Falconi]

the problem persists, "ip mtu" command 

Router#SH RUN int bdi 50
Building configuration...

Current configuration : 75 bytes
!
interface BDI50
 ip address 20.20.20.1 255.255.255.252
 ip mtu 1600
end

Router#ping 20.20.20.2 si
Router#ping 20.20.20.2 size 1501 df
Type escape sequence to abort.
Sending 5, 1501-byte ICMP Echos to 20.20.20.2, timeout is 2 seconds:
Packet sent with the DF bit set
.....
Success rate is 0 percent (0/5)
Router#ping 20.20.20.2 size 1500 df
Type escape sequence to abort.
Sending 5, 1500-byte ICMP Echos to 20.20.20.2, timeout is 2 seconds:
Packet sent with the DF bit set
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms
Router#sh int bdi 50 | i MTU
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
Router#

[bhnegi]

Hi Peter,

what is the  mtu configured on 20.20.20.2?

What is the configuration of the underlying layer 2 port which is configured for bridge domain 50? Have you increased the MTU there?

Also please do "sh ip int bdi 50 | i MTU" not "sh int bdi 50 | i MTU".

Best Regards,

Bheem

[filopeter]

here is my partial configuration, you need also to increase the mtu on a physical interface 

!
interface BDI20
 ip address 192.168.1.1 255.255.255.0
 ip mtu 1512
!
interface GigabitEthernet0/0/4
 mtu 1512
 no ip address
 media-type auto-select
 negotiation auto
 service instance 10 ethernet
  encapsulation untagged
  bridge-domain 20
!
R2#ping 192.168.1.10 size 1512 df
Type escape sequence to abort.
Sending 5, 1512-byte ICMP Echos to 192.168.1.10, timeout is 2 seconds:
Packet sent with the DF bit set
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms