From: Joseph D. Phillips (josephdphillips@fastmail.us)
Date: Wed Sep 15 2004 - 20:56:30 GMT-3
I was wondering what current ISP practice is regarding hot-potato vs.
cold-potato routing.
According to one article I read, ISPs sort of go right down the middle
-- not trying to get rid of traffic right away and not trying to do too
much QoS on it, either.
James wrote:
>On Thu, Sep 16, 2004 at 12:01:00AM +0200, Joseph Rothstein wrote:
>
>
>>Hi Guys,
>>
>>I know what the problem is, but I am not sure how I get the results that I do compared to the author's.
>>
>>As far as BGP path selection goes, I believe that the path selection comes down to number, 10, and does not go to 12.
>>
>>"10. Prefer the route that can be reached through the closest IGP neighbor...." Although I am not sure if this applies to external routes as wella sinternal.
>>
>>
>
>eBGP routes are preferred over iBGP routes before the IGP cost issue.
>
>BGP by default has what we call "hot potato" behaviour, where a default configuration
>will always seek out closest exit point to leave the local AS. So when you have iBGP,
>nexthop with smallest igp cost is preferred. Likewise, when you have iBGP and eBGP,
>eBGP is preferred.
>
>
>
>>In this case, since the IGP section asks you to manipulate the bandwidth of the links between R1-R4 and R6-R4, 256 ans 512 respectively, the preferred path is to 10.6.6.6 like the bgp table shows since it has the lower OSPF metric.
>>
>>
>
>What is the active igp path on R6 to get to 10.90.90.x? Does it go over the
>Ethernet instead?
>
>Do a 'sh ip route 10.90.90.1' on R4, R6, R1 so we can see the cost of that route.
>Also doing 'sh ip bgp 2.2.2.0' on all 3 routers would give us more information such
>as the metric derived from RIB for the next hop.
>
>HTH,
>-J
This archive was generated by hypermail 2.1.4 : Fri Oct 01 2004 - 15:00:44 GMT-3