From: Nordhoff, Michael G. (US - Hermitage) (mnordhoff@deloitte.com)
Date: Wed Sep 10 2003 - 18:36:55 GMT-3
Thanks for the clarification. The intent is to minimize the potential for
asymmetrical routing that will most likely occur when the 2 ISPs I will be
peering with connect to the same peering points beyond their AS's. For
example, I peer with Provider A and Provider B. Provider A and Provider B
both peer with Provider C. My intent was to ultimately influence the path
Provider C takes back to me. Perhaps it was a good idea but not easily
implemented...
Thanks again for the feedback...
- MN
-----Original Message-----
From: Rob Laidlaw [mailto:laidlaw@consecro.com]
Sent: Wednesday, September 10, 2003 4:11 PM
To: Nordhoff, Michael G. (US - Hermitage); ccielab@groupstudy.com
Subject: Re: BGP Question Concerning MED attribute
Routing TCP/IP vol.2, page 246.
"When a BGP speaker learns a route from a peer, it can pass the route's
MED to any IBGP peers, but not to EBGP peers. As a result, the MED has
relevance only between neighboring autonomous systems."
I don't believe there is anything you can do to pass this attribute. Why do
you want to pass this information? Its function is to allow a customer with
multiple connection to the same provider to pick their entry point. If BGP
passed this info to the ISP's external neighbors, then the customer would be
able to choose paths in the ISP's network rathern then the ISP.
Rob
----- Original Message -----
From: "Nordhoff, Michael G. (US - Hermitage)" <mnordhoff@deloitte.com>
To: <ccielab@groupstudy.com>
Sent: Wednesday, September 10, 2003 3:39 PM
Subject: BGP Question Concerning MED attribute
> A quick question concerning the BGP MED attribute...
>
>
>
> Is it normal behavior for a BGP peer to NOT pass along MED information for
> prefixes learned from BGP peers in different AS's? My scenario is this...
> R1 is attached to R2. R3 is attached to R4. R2 and R4 are attached to
R5.
> R1 advertises a prefix to R2 via EBGP as does R3 to R4. R2 and R4 then
> advertise these prefixes to R5 via EBGP. The MED attributes added by R1
and
> R3 are received by R2 and R4, respectively. However, these MEDs are not
> being passed along to R5. What is the reason for this behavior and what
can
> be done to circumvent it?
>
>
>
> Thanks in advance!
>
>
>
> Mike Nordhoff - CCNP,CCDP
>
> Deloitte & Touche, National WAN Services
>
>
>
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