Re: PBR and TOS

In article <ffgap21cfefa1brhn54528lcj0lkuephl8@xxxxxxx>,
Bob Simon <nobody@xxxxxxxxxxx> wrote:
Packets from one specific interface on a 1711 at a remote site need to
be tagged so they can be routed differently by a 3745 at headquarters.
I've started reading about Policy Based Routing and it looks like this
technology will enable me to solve this problem. Are there any cavets
that I should know about before I begin a design?

Neither QoS nor high-priority queueing are deployed in this network at
present but I want to avoid tagging the packets in such a way that
would conflict with VoIP and other standards.

Should I use IP TOS or IP Precedence to tag these packets? If IP
Precendece is the way to go, is there any reason to set or avoid the
value 1 (priority) vs 2 (immediate), vs 3 (flash)?

Do you have a leased line, or do you have an end-to-end contract
with the ISP(s) involved? If you do not, if the packets are flowing
over the internet, then as best I recall, it would not be invalid
for those bits to be rewritten by intermediate hops (which,
after all, might need to use them to give your packets the proper
internal priorities in transit.) If you do not have a direct link
or MLPS, then if you want to tag the packets at one location
and have the tags read at a remote location, you are going to
need to do some kind of encapsulation between the two points.
Thta could be via GRE, or could be (e.g.) by using an 802.1Q vlan
inside an IPSec tunnel.


If the packets are from a different interface, then the implication
would be that they have different original source IP addresses.
Is there a reason why you can't have the far end differentiate
based upon source IPs? If you are NAT'ing, perhaps you could
NAT into different IP ranges?
.