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GRE and PAK_Priority

Unanswered Question
Apr 21st, 2010
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Within a router, Is PAK_Priority preserved once a packet is encapsulated in GRE? In other words, if a EIGRP packet had PAK_priority set and was then encapsulated in GRE, does the GRE packet now have PAK_priority set?

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Jon Marshall Wed, 04/21/2010 - 14:38
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danieweber wrote:


Within a router, Is PAK_Priority preserved once a packet is encapsulated in GRE? In other words, if a EIGRP packet had PAK_priority set and was then encapsulated in GRE, does the GRE packet now have PAK_priority set?


Daniel


PAK_priority marks routing protocols to DSCP CS6 so once the packet has been encapsulated in a GRE header then the header will have the DSCP value but obviously it is then up to the intermediate routers to honour that value.


Jon

Dan Weber Wed, 04/21/2010 - 14:46
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Jon,


Thanks for the quick response. I knew that all routing protocols get marked to CS6, but I thought that PAK_Priority was an additional internal flag that was used within a router to ensure those packets were forwarded on a congested interface. The question I have is, if the original EIGRP packet had the PAK_priority flag, does that carry to the GRE packet that ultimately gets forwarded out the interface?

Jon Marshall Wed, 04/21/2010 - 14:50
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danieweber wrote:


Jon,


Thanks for the quick response. I knew that all routing protocols get marked to CS6, but I thought that PAK_Priority was an additional internal flag that was used within a router to ensure those packets were forwarded on a congested interface. The question I have is, if the original EIGRP packet had the PAK_priority flag, does that carry to the GRE packet that ultimately gets forwarded out the interface?


Sorry, i didn't explain it very well.


PAK_Priority is indeed an internal flag that tells the local router what to do with this packet if the interface is congested.  This is not copied to the GRE header. What is copied is the CS6 value but only the router at the other end of the GRE tunnel will actually see the PAK_Priority in the initial packet once the GRE header has been removed.


Jon

Dan Weber Fri, 04/23/2010 - 08:05
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Jon, I thought that PAK_priority was an internal flag used by the router and not used externally. Can you confirm that the other GRE endpoint would see the PAK_priority flag after the GRE header is removed?

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