QOS definitions for Routing Protocols over WAN/VPN's

Answered Question
Apr 10th, 2007

I need to know whether OSPF LSA updates have a default DSCP or TOS bit (or any other QOS marking) predefined on them, and whether default QOS policy-maps and class-maps define prioritization for routing protocol updates or whether they need be marked and QOS defined.

If manual marking of routing protocols is required, what DSCP should be defined for IPSEC VPN tunnel traffic?

Thanks,

-Scott

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Correct Answer by Harold Ritter about 9 years 9 months ago

Routing protocols are generally marked with an IP precedence value of 6 (Network Control). It is a good idea to reserve some bandwidth so that these packets are not dropped in case of congestions.

Hope this helps,

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Correct Answer
Harold Ritter Tue, 04/10/2007 - 12:50

Routing protocols are generally marked with an IP precedence value of 6 (Network Control). It is a good idea to reserve some bandwidth so that these packets are not dropped in case of congestions.

Hope this helps,

swharvey Tue, 04/10/2007 - 14:08

Thanks that helps quite a bit! I'll check the document out, but off the cuff, how much bandwidth should be allocated for ospf hellos, and should bandwidth be allocated for the database propagation updates (which vary and use large mtu's).

Thanks,

-Scott

sundar.palaniappan Tue, 04/10/2007 - 14:13

Just want to add to Harold's post that, by default, you can only allocate only 75% of the available bandwidth on an interface. The other 25% is reserved for all management traffic including routing protocol traffic. If you want to allocate more than 75% you need to use the interface command 'max-reserved-bandwidth (%)'.

HTH

Sundar

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