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New Member

LDP

Hi,

can a router have 2 different LDP sessions to the another router (through 2 physical interfaces) ?

Thank you

5 REPLIES
Cisco Employee

Re: LDP

You will only have a single TCP session no matter how many parallel physical links there is between the two adjacent routers.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: LDP

Hi thanks!

will the TCP session always take place across the same link ?

Cisco Employee

Re: LDP

The TCP session is normally between the adjacent routers loopback interface addresses and is subjected to the normal CEF switching process.

This means that if you have several physical links, CEF will decide which link to choose for this specific flow.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Re: LDP

Hello,

just a small addition: what Harold said is true for frame-mode MPLS. In cell-mode MPLS (MPLS enabled ATM switches and routers) there can be two LDP sessions or more. The design decision afaik was to have one LDP session per label space.

In frame-mode MPLS there is only one label space :0 hence only one LDP session.

In cell-mode MPLS there is one label space per ATM interface - label space :1,2,3,... labels used: VPI/VCI values - hence there can be many LDP sessions (one per interface).

Hope this helps! Please rate all posts.

Regards, Martin

New Member

Re: LDP

OK. Just what I needed. thank you to both!

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