Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

MTU Cisco and Juniper

Hello we have site to site connetions on a layer2 domain.

So

cisco3560<----Layer 2 Hardware Encrytor-->ME3400-2CS-A<---Dot1Q tunnel--->ME3400-2CS-A<---LAyer 2 Hardware Encryptor---->Juniper EX 4200

I-am receiving Latencies from copynig from clients on juniper to clients to Cisco. The other side is ok.

MTU Jumbo on ME 3400 is 1800. Link is Gigabit. I havent changed the mtu on Encryptor and on Cisco nor Juniper .

As I googled and saw Juniper and Cisco have diffrent MTU 1518 on Juniper and 1500 on Cisco.

On Wireshirek I see TCP Previous segment lost, TCP Duplicate and TCP Fast retranssmission.

Any advice for this situation you think this is Fiber problem or MTU.

To be Clear everything worked k isnce two weeks before

Regards

5 REPLIES
Hall of Fame Super Silver

Re: MTU Cisco and Juniper

Hello Enkli,

on EX 4200 1518 refers to the L2 MTU that is the ethernet frame size, so this shouldn't be a problem as ip mtu is 1500 bytes for both

Hope to help

Giuseppe

New Member

Re: MTU Cisco and Juniper

Giuslar thank you very much for you reply.

To be more clear. The design is like that

(A)C3560<-->Hardware encryptor<--->dot1Q ME3400G<--DarkFiber-->dot1Q ME3400G<--->Hardware encryptor<--->C3560(B)

                                                                                                              ^

                                                                                                              |

                                                                                                              |

                                                                                                         DarkFiber

                                                                                                              |

                                                                                                         Dot1Q ME3400G

                                                                                                              |

                                                                                                    Hardware encryptor

                                                                                                              |

                                                                                                 Juniper EX4200(C)


Everything was fine before

Now I am able to copy in full speed from any computer at site C to/from site B and vice versa

Now I am able to copy in full speed from any computer at site A to/from site B and vice versa

Bu I can copy form site C and A but I am not able to cop[y to site A. I see loss of packets even inside VLAN

Have you any idea her might be the problem in the interconnecting switch ME3400 at junipers might be some loop cause i dont see packets on trunk interface of Juniper outgoing just 1 or 2 Mbps. I have done test on fiber from telecom and they say it is fine.

Regards

Enkli

VIP Super Bronze

Re: MTU Cisco and Juniper

Hi Enkli,

What type of encryption device are you using?

Reza

New Member

Re: MTU Cisco and Juniper

I dont think there might be a problem. we are using Cipherop

tics layer 2 encryptors

New Member

Re: MTU Cisco and Juniper

Do you have problem from site A to C? Have you bypassed encryptors to make sure about them? Have you measured path MTU by ping and setting DF value?

1672
Views
0
Helpful
5
Replies