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ilucas
New Contributor

Comcast DSCP trouble?

I've done some research on posts (non fortinet forums) that list the DSCP bits coming from comcast to the local modem/installation as the lowest priority (0x08) and that to fix this I've typically seen commands to make iptables essentially convert those dscp bits to 0x00 to unclassify the incoming traffic and process it without that interference.

 

Has anyone ever implemented this with FortiGate, if they are even affected?

I unfortunately do not have a unit and an open comcast connection to play around with.

 

This is the command I've seen recommended to implement, if it helps:

iptables -t mangle -A PREROUTING -i vlan2 -j DSCP --set-dscp 0

----

FG 200B/30D/60D/80D/100D/200D/300D

FE 200D

---- FG 200B/30D/60D/80D/100D/200D/300D FE 200D
10 REPLIES 10
emnoc
Esteemed Contributor III

Will if the  L3 header is set for  DSCP, they should be zero'd upon  arrived and any  cisco switch  ( for example ) will zero  out the dscp also, unless the port is  "trusted". The same for juniper EX, and I would expect a host of others.

 

 

My thoughts,

 

what value are you seeing w/DCSP  ( hex 0x08  )?

 

have you dump the packets on the egress interface into your cust_LAN for example? and if yes, what do you see?

 

Ken

PCNSE 

NSE 

StrongSwan  

PCNSE NSE StrongSwan