How is negociated MAX PDU length between a Cisco and Huawei switch Highlighted

Latest reply: Dec 26, 2018 15:31:48 359 2 0 0
Issue Description

Device : Quidway S7703

Version: V200R008C00SPC500

We are going to merge 2 big networks ; The first is a Huawei network (150 switchs mpls) and the second is a Cisco Network (100 routers). IGP on Huawei is OSPF and on Cisco is ISIS. We will deploy ISIS gradually on our Huawei network.

And we need to understand how the interconnection works, because there are many customers on these networks so we will use for test a MPLS between a Cisco-7606 and Huawei S7700.

When we use full Huawei network, we can view “Initialization Message’’. When we use full Cisco network, we can view “Initialization message’’. But, when we use Huawei and Cisco network, we don’t view “initialization message”.

On Full Cisco Network, Max PDU Length is 0. On Full Huawei Network, Max PDU Length is 4096. We need to know if that is a problem in the future, if we use the both on the same network.

So main questions are :

1. How is negociated MaxPDU length when the value for the first router is 0 (Cisco) and the second router is 4096 (Huawei)?

2. How can we display that MaxPDU was negociated ?

63d885e2a34e4bf6aab0d8d9c0bda535


transparent.gif Alarm Information

No alarm present, we noticed just the Initialization message was not present at the begining.


4c9682b0e0d141ad9f30002723d31e9f

transparent.gif Handling Process

Checking the Init message in terminal of Huawei :

 Sep 29 2017 11:51:06.860.1+02:00 DST LAB-S77 LDP/7/PDU:  

 11:1546: Receive TCP Message from Peer: 192.168.95.25. Message content: 

 02 00 00 16 00 09 7d 99 05 00 00 0e 00 01 00 b4

 00 00 00 00 c0 a8 5f 17 00 00

 The message type: Initialization Message..

<LAB-S77>

Sep 29 2017 11:51:06.860.2+02:00 DST LAB-S77 LDP/7/PDU:  

 11:3812: LDP msg added to ssn's nor-msg-list. (MsgType:0x200|0x0, Ssn:192.168.95.25)

<LAB-S77>

Sep 29 2017 11:51:06.860.3+02:00 DST LAB-S77 LDP/7/PDU:  

 11:3894: Send TCP Message to Peer: 192.168.95.25. Message content: 

 02 00 00 16 00 57 b0 27 05 00 00 0e 00 01 00 2d

 00 00 10 00 c0 a8 5f 19 00 00

 The message type: Initialization Message..

<LAB-S77>

2. Checking the MPLS LDP peer :

<LAB-S77>dis mpls ldp peer

 

 LDP Peer Information in Public network

 A '*' before a peer means the peer is being deleted.

 ------------------------------------------------------------------------------

 PeerID                 TransportAddress   DiscoverySource

 ------------------------------------------------------------------------------

 192.168.95.25:0        192.168.95.25      Vlanif4088

 ------------------------------------------------------------------------------

 TOTAL: 1 Peer(s) Found.

Checking the MPLS LDP session :

<LAB-S77>dis mpls ldp session

 

 LDP Session(s) in Public Network

 Codes: LAM(Label Advertisement Mode), SsnAge Unit(DDDD:HH:MM)

 A '*' before a session means the session is being deleted.

 ------------------------------------------------------------------------------

 PeerID             Status      LAM  SsnRole  SsnAge      KASent/Rcv

 ------------------------------------------------------------------------------

 192.168.95.25:0    Operational DU   Passive  0000:00:07  29/34

 ------------------------------------------------------------------------------

 TOTAL: 1 session(s) Found.

Checking also MPLS LSP :

5f458261c9b34a519f6647cf54ab8b45

Checking also the l2vc  and is up:

7b18f92da51f483dae1cf7322155ee56


transparent.gif Root Cause

For the first issue, the root cause was that the Init message arrive during a different path and the negotiated value works like this: from the RFC we select the small value. But if the value is below 255.  RFC rule use the default value 4096.


transparent.gif Solution

Question 1 answer : 

It chooses the smaller one (if the peer value is zero we will use the local value).


f996495432be4176b1ef0d7178befdec


Question 2 answer:

We can use command below :

1. For Huawei vs Huawei:

[S6720EI-20.21-diagnose]dis mpls ldp peer verbose                                                                                       

                                                                                                                                    

 LDP Peer Information in Public network                                                                                             

 ------------------------------------------------------------------------------                                                    

 Peer LDP ID         : 1.1.1.40:0                                                                                                   

 Peer Max PDU Length : 4096         Peer Transport Address : 1.1.1.40                                                              

 Peer Loop Detection : Off          Peer Path Vector Limit : ----                                                                  

 Peer FT Flag        : Off          Peer Keepalive Timer   : 45 Sec                                                                

 Recovery Timer      : ----         Reconnect Timer        : ----                                                                  

 Peer Type           : Local                                                                                                       

                                                                                                                                    

 Peer Label Advertisement Mode : Downstream Unsolicited                                                                            

 Peer Discovery Source         : Vlanif2                                                                                           

 Peer Deletion Status          : No                                                                                                

 Capability-Announcement       : Off                                                                                               

 Peer mLDP P2MP Capability     : Off                                                                                                

 Peer mLDP MP2MP Capability    : Off                                                                                               

 Peer mLDP MBB Capability      : Off                                                                                                

 ------------------------------------------------------------------------------                                                    

2. For Huawei vs CISCO                                                                                                                          

[S6720EI-20.21-diagnose]

<LAB-S77>dis mpls ldp peer verbose

 

 LDP Peer Information in Public network

------------------------------------------------------------------------------

Peer LDP ID         : 192.168.95.25:0

Peer Max PDU Length : 0            Peer Transport Address : 192.168.95.25

Peer Loop Detection : Off          Peer Path Vector Limit : ----

Peer FT Flag        : Off          Peer Keepalive Timer   : 180 Sec

Recovery Timer      : ----         Reconnect Timer        : ----

Peer Type           : Local&Remote

 

Peer Label Advertisement Mode : Downstream Unsolicited

Peer Discovery Source         : remote peer: 192.168.95.25

                                 Vlanif4088

Peer Deletion Status          : No

Capability-Announcement       : Off

Peer mLDP P2MP Capability     : Off

Peer mLDP MP2MP Capability    : Off

Peer mLDP MBB Capability      : Off

------------------------------------------------------------------------------


  • x
  • convention:

xiaomumu Created Dec 24, 2018 09:40:39 Helpful(0) Helpful(0)

Learn more, great
  • x
  • convention:

dagui Created Dec 26, 2018 15:31:48 Helpful(0) Helpful(0)

For the first issue, the root cause was that the Init message arrive during a different path and the negotiated value works like this: from the RFC we select the small value. But if the value is below 255. RFC rule use the default value 4096.Can you provide a more detailed explanation?

  • x
  • convention:

Reply

Reply
You need to log in to reply to the post Login | Register

Notice: To protect the legitimate rights and interests of you, the community, and third parties, do not release content that may bring legal risks to all parties, including but are not limited to the following:
  • Politically sensitive content
  • Content concerning pornography, gambling, and drug abuse
  • Content that may disclose or infringe upon others ' commercial secrets, intellectual properties, including trade marks, copyrights, and patents, and personal privacy
Do not share your account and password with others. All operations performed using your account will be regarded as your own actions and all consequences arising therefrom will be borne by you. For details, see " Privacy."
If the attachment button is not available, update the Adobe Flash Player to the latest version!

Login and enjoy all the member benefits

Login
Fast reply Scroll to top