Mailing List Archive

MTU problem Brocade Chassis: MLXe 4-slot
Hi,

We need to setup an L2 connection with MTU=1540 for a customer. After changing default-max-frame-size to 2000 and issue reload, we still can't get replies to icmp with size > 1500 bytes and df-bit set.


1510 Byte, DF not set = OK
=================================
hostname#ping x.x.x.x size 1510
Type escape sequence to abort.
Sending 5, 1510-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/7/8 ms



1511 Byte DF not set = not OK
=================================
hostname#ping x.x.x.x size 1511
Type escape sequence to abort.
Sending 5, 1511-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

1500 Byte, DF set = OK
=================================
hostname#ping x.x.x.x size 1500 df-bit
Type escape sequence to abort.
Sending 5, 1500-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
Packet sent with the DF bit set
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/8 ms


1501 Byte, DF set = not OK
=================================
hostname#ping x.x.x.x size 1501 df-bit
Type escape sequence to abort.
Sending 5, 1501-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
Packet sent with the DF bit set
.....
Success rate is 0 percent (0/5)


#show max-frame-size
Default max frame size for ETH : 2000
Default max frame size for POS : 4474
Slot 1 Port 1 Port 2 Port 3 Port 4
-------- -------- -------- --------
2000 2000 2000 2000

Port 5 Port 6 Port 7 Port 8
-------- -------- -------- --------
2000 2000 2000 2000

Port 9 Port 10 Port 11 Port 12
-------- -------- -------- --------
2000 2000 2000 2000

Port 13 Port 14 Port 15 Port 16
-------- -------- -------- --------
2000 2000 2000 2000

Port 17 Port 18 Port 19 Port 20
-------- -------- -------- --------
2000 2000 2000 2000

Slot 2 Port 1 Port 2 Port 3 Port 4
-------- -------- -------- --------
2000 2000 2000 2000

Port 5 Port 6 Port 7 Port 8
-------- -------- -------- --------
2000 2000 2000 2000

Port 9 Port 10 Port 11 Port 12
-------- -------- -------- --------
2000 2000 2000 2000

Port 13 Port 14 Port 15 Port 16
-------- -------- -------- --------
2000 2000 2000 2000

Port 17 Port 18 Port 19 Port 20
-------- -------- -------- --------
2000 2000 2000 2000

Slot 3 Port 1 Port 2 Port 3 Port 4
-------- -------- -------- --------
2000 2000 2000 2000

Slot 4 Port 1 Port 2 Port 3 Port 4
-------- -------- -------- --------
2000 2000 2000 2000

Port 5 Port 6 Port 7 Port 8
-------- -------- -------- --------
2000 2000 2000 2000

Port 9 Port 10 Port 11 Port 12
-------- -------- -------- --------
2000 2000 2000 2000

Port 13 Port 14 Port 15 Port 16
-------- -------- -------- --------
2000 2000 2000 2000

Port 17 Port 18 Port 19 Port 20
-------- -------- -------- --------
2000 2000 2000 2000


Is there anything else to be changed to accomplish this?

Best regards,

Adrian Luchian
Re: MTU problem Brocade Chassis: MLXe 4-slot [ In reply to ]
Hi Adrian,

maybe I am late to the party, but seems your configuration works.

1510 + IP + ICMP => 1538 bytes
1511 + IP + ICMP + 3 bytes padding => 1542 (wont work)

Regards
Jörg

On 28 Feb 2017, at 12:50, Adrian Luchian wrote:

> Hi,
>
> We need to setup an L2 connection with MTU=1540 for a customer. After
> changing default-max-frame-size to 2000 and issue reload, we still
> can't get replies to icmp with size > 1500 bytes and df-bit set.
>
>
> 1510 Byte, DF not set = OK
> =================================
> hostname#ping x.x.x.x size 1510
> Type escape sequence to abort.
> Sending 5, 1510-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
> !!!!!
> Success rate is 100 percent (5/5), round-trip min/avg/max = 4/7/8 ms
>
>
>
> 1511 Byte DF not set = not OK
> =================================
> hostname#ping x.x.x.x size 1511
> Type escape sequence to abort.
> Sending 5, 1511-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
> .....
> Success rate is 0 percent (0/5)
>
> 1500 Byte, DF set = OK
> =================================
> hostname#ping x.x.x.x size 1500 df-bit
> Type escape sequence to abort.
> Sending 5, 1500-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
> Packet sent with the DF bit set
> !!!!!
> Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/8 ms
>
>
> 1501 Byte, DF set = not OK
> =================================
> hostname#ping x.x.x.x size 1501 df-bit
> Type escape sequence to abort.
> Sending 5, 1501-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
> Packet sent with the DF bit set
> .....
> Success rate is 0 percent (0/5)
>
>
> #show max-frame-size
> Default max frame size for ETH : 2000
> Default max frame size for POS : 4474
> Slot 1 Port 1 Port 2 Port 3 Port 4
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 5 Port 6 Port 7 Port 8
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 9 Port 10 Port 11 Port 12
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 13 Port 14 Port 15 Port 16
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 17 Port 18 Port 19 Port 20
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Slot 2 Port 1 Port 2 Port 3 Port 4
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 5 Port 6 Port 7 Port 8
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 9 Port 10 Port 11 Port 12
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 13 Port 14 Port 15 Port 16
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 17 Port 18 Port 19 Port 20
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Slot 3 Port 1 Port 2 Port 3 Port 4
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Slot 4 Port 1 Port 2 Port 3 Port 4
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 5 Port 6 Port 7 Port 8
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 9 Port 10 Port 11 Port 12
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 13 Port 14 Port 15 Port 16
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
> Port 17 Port 18 Port 19 Port 20
> -------- -------- -------- --------
> 2000 2000 2000 2000
>
>
> Is there anything else to be changed to accomplish this?
>
> Best regards,
>
> Adrian Luchian