From: Devi Mallampalli (Devi.Mallampalli@chubb.com.au)
Date: Tue May 04 2004 - 01:18:39 GMT-3
Hi Sergio,
When you originate a BGP route sourced from an IGP , then IGP's metric
is converted to BGP MED by default. However if the route is local to the
router the MED is by default "0" when you inject that route in to EBGP.
The cmd (set metric-type internal) in BGP will enable the MED values on
prefixes advertised to EBGP peer to match the IGP metric of the next
hop. If this command is used, multiple BGP speakers in a common
autonomous system can advertise different MED values ( If multihoming
with multiple ISPs and peering with one ISP at multiple points, use "bgp
deterministic-med" and enable it on all routers in the AS . And this
will ensure the comparison of "MED variable" when choosing routes
advertised by different peers in the same AS)for a particular prefix.
Also, note that if the IGP metric changes, BGP will readvertise the
route every 10 minutes.
Hope this helps in terms of what this command does in BGP.
Regards
Devi.
-----Original Message-----
From: Sergio Jimenez Arguedas [mailto:sejimenez@its.co.cr]
Sent: Tuesday, 4 May 2004 4:45 AM
To: ccielab@groupstudy.com
Subject: Fw: BGP MED Scenario!!!-2nd try
Hi Devi,
I agree with you, but the doubt is the following:
___________________________________
Hi,
Mohamed, I really did it, but WITHOUT the route-map INT SFM Tx the
prefix to Side with the eigrp metric.
So, I got confused with that cmd (set metric-type internal) in BGP.
___________________________________
Thanks for your time!!!
Sergio
----- Original Message -----
From: "Devi Mallampalli" <Devi.Mallampalli@chubb.com.au>
To: "Mohamed" <nmohamed@cisco.com>; <ccielab@groupstudy.com>
Sent: Monday, May 03, 2004 7:25 AM
Subject: RE: BGP MED Scenario!!!-2nd try
> Hi Sergio & Mohamed,
>
> Let me understand this me being a late comer/listener to this Hi,
> >
> > Mohamed, I really did it, but WITHOUT the route-map INT SFM Tx the
> > prefix to Side with the eigrp metric.
> >
> > So, I got confused with that cmd (set metric-type internal) in BGP.
> conversation.
>
> Down---------------SFM-----------Side---------Up . In this topology,
> Down and SFM are running "eigrp" between them and SFM and "side" are
> running BGP between them. And you are "not" redistributing IGP in to
> Side from SFM and instead you want to publish the "inbound" IGP
> networks from Down to SFM in to the "BGP" Process at SFM. And you want
> to EIGRP routes of 200.100.100.0/24 appear at "side" as internal
> routes with the help of Router-maps & internal metric types.
>
> This is the scenario , right ?
>
> Honestly speaking with my very limited knowledge of BGP, I did not
> come across manipulating routes with the help of "metric-type"
> internal. Indeed I was in impression this kind of "metric-external
> types" (Type 1 and type 2) feature is more to do with "OSPF" when you
> want to influence incoming external routes from ASBR.
>
> But when you look at your below config & outputs , I kind of agree
> with Mohamed that the route map is doing what she is suppose to do and
> as result on "side " you are indeed seeing the "inbound" eigrp route
> as IGP ( "I")
>
> 200.100.100.0 99.99.99.1 128512 0 100 I >>>>
>
> Am I thinking on right lines here ? Please elaborate the issue if you
> can.
>
> On another note from LAB exam point of view , Determining the BGP
> filtering policy (what do you want to do or what author wants to
> achieve) is more critical along with which router or interface to
> apply the policy on and the configuration part is relatively easier.
> personally speaking, I try to be little cautious in getting what the
> policy should be based on the question and more importantly where to
> apply the BGP's knobs & twiddles ( ex: AS Path prepending is always
> "out" , "community is always "out" , MED is always "out" , Local
> Preference is always "In" and Weight is always "out"...etc) as it is
> very easy to commit a mistake.
>
> Regards
>
> Devi....
>
> -----Original Message-----
> From: Mohamed [mailto:nmohamed@cisco.com]
> Sent: Monday, 3 May 2004 7:05 PM
> To: ccielab@groupstudy.com
> Subject: RE: BGP MED Scenario!!!-2nd try
>
>
> Hi all,
>
> 2nd try, can anyone help on this!!
>
> Thanks
> Mohamed.
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Sergio Jimenez Arguedas
> Sent: Friday, April 30, 2004 8:35 PM
> To: ccielab@groupstudy.com
> Subject: Fw: BGP MED Scenario!!!
>
>
> Hi Group
>
> Is someone able to help us, please?
>
>
> Rgds,
>
> Sergio Jiminez A.
>
>
> ----- Original Message -----
> From: "Mohamed" <nmohamed@cisco.com>
> To: "'Sergio Jimenez Arguedas'" <sejimenez@its.co.cr>;
> <ccielab@groupstudy.com>
> Sent: Friday, April 30, 2004 12:10 AM
> Subject: RE: BGP MED Scenario!!!
>
>
> > Hi,
> > Sergio,
> > Yeah, really I also don't know,hope someone would be able to help
> > us..
> >
> >
> > Thanks
> > Mohamed.
> >
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of Sergio Jimenez Arguedas
> > Sent: Thursday, April 29, 2004 8:27 PM
> > To: ccielab@groupstudy.com
> > Subject: Fw: BGP MED Scenario!!!
> >
> >
> >> >
> > Thanks,
> > Sergio
> >
> >
> > ----- Original Message -----
> > From: "Mohamed" <nmohamed@cisco.com>
> > To: "'Sergio Jimenez Arguedas'" <sejimenez@its.co.cr>;
> > <ccielab@groupstudy.com>
> > Sent: Thursday, April 29, 2004 12:56 AM
> > Subject: RE: BGP MED Scenario!!!
> >
> >
> > > Hi,
> > > I got your question, sorry I couldnot spare time to do in OSPF!.
> > >
> > > SFM#sh ip route eigrp
> > > 20.0.0.0/24 is subnetted, 1 subnets
> > > D 20.1.1.0 [90/28416] via 25.25.25.26, 00:01:31,
> FastEthernet3/6
> > > 200.100.100.0/24 is variably subnetted, 2 subnets, 2 masks
> > > D 200.100.100.0/24
> > > [90/128512] via 25.25.25.26, 00:01:31, FastEthernet3/6
> > > 201.100.100.0/24 is variably subnetted, 2 subnets, 2 masks
> > > D 201.100.100.0/24
> > > [90/128512] via 25.25.25.26, 00:01:31, FastEthernet3/6
> > >
> > > Note the metric on eigrp route-128512 for network 200.100.100.0/24
> > >
> > > Now -
> > > SFM#sh run | b router bgp
> > > router bgp 100
> > > no synchronization
> > > bgp log-neighbor-changes
> > > network 200.100.100.0 <<<<<<<<<<<<<<<<
> > > network 201.100.100.0 <<<<<<<<<<<<<<<<<
> > > neighbor 25.25.25.26 remote-as 100
> > > neighbor 99.99.99.2 remote-as 300
> > > neighbor 99.99.99.2 route-map INT out
> > > no auto-summary
> > >
> > > So here iam advertising network 200.100.100.0.
> > >
> > > Down---------------SFM-----------Side---------Up
> > >
> > > From down to sfm router,I run eigrp and down advertise
> > > 200.100.100.0
>
> > > and 201.100.100.0 as eigrp routes to sfm router. I DON'T
> > > REDISTRIBUTE EIGRP HERE!!!! In SFM. I advertise using network
> > > command.I set a route-map to Side router. Now see what the
> > > route-map
>
> > > is
> > >
> > >
> > > ip as-path access-list 9 permit .*
> > > route-map INT permit 10
> > > match as-path 9
> > > set metric-type internal
> > > End
> > >
> > >
> > > So BGP set the metric of the advertised routes 200.100.100.0 and
> > > 201.100.100.0 to Side as Eigrp metric=128512 . Side#sh ip bgp BGP>
> > table version is 78, local router ID is 213.1.4.1 Status codes: s
> > > suppressed, d damped, h history, * valid, > best, i - internal
> > > Origin codes: i - IGP, e - EGP, ? - incomplete
> > >
> > > Network Next Hop Metric LocPrf Weight Path
> > > *> 200.100.100.0 99.99.99.1 128512 0 100 i
> > > *> 201.100.100.0 99.99.99.1 128512 0 100 i
> > > Side#
> > >
> > > I think it don't do anyother job than this!!
> > >
> > > Thanks
> > > Mohamed.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > > Behalf
>
> > > Of Sergio Jimenez Arguedas
> > > Sent: Wednesday, April 28, 2004 10:08 PM
> > > To: ccielab@groupstudy.com
> > > Subject: Fw: BGP MED Scenario!!!
> > >
> > >
> > > Hi Mohamed,
> > >
> > >
> > > I really understand that, but the doubt is the following,
> > >
> > > 172.16.0.0------RA-------------RB-------------RC-------------RD
> > >
> > >
> > > Config RB
> > >
> > >
> > > router bgp 1
> > > netw 172.16.0.0
> > > neighbor x.x.x.x remote-as 2
> > >
> > >
> > > RBsi
> > > Tx the prefix if it has a route of 172.16.0.0 in the routing
> > > table.
>
> > > RB Rx the route from RA by ospf, So RB tx the prefix with the IGP
> > > metric to RC without THE ROUTE-MAP with set metric-type internal.
> > >
> > >
> > > Question: How can I use a route-map with set metric-type internal?
> > >
> > >
> > > Thanks,
> > >
> > >
> > > Sergio
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > ----- Original Message -----
> > > From: "Mohamed" <nmohamed@cisco.com>
> > > To: "'Sergio Jimenez Arguedas'" <sejimenez@its.co.cr>;
> > > <ccielab@groupstudy.com>
> > > Sent: Wednesday, April 28, 2004 1:20 AM
> > > Subject: RE: BGP MED Scenario!!!
> > >
> > >
> > > > I tried in my router,
> > > >
> > > > A----------B----------C---------D
> > > >
> > > > A,B are IBGP,running OSPF.
> > > > B redistributing OSPF into BGP.
> > > > C is EBGP of B.
> > > > D is Ebgp of C
> > > >
> > > > Now in C,we get the metrics from B,bcoz C only reset the metric
> > > > to
>
> > > > zero. In D we don't get metric.
> > > >
> > > >
> > > > Now if u put route-map and set metric-type int or even set
> > > > origin igp,I don't get any mteric in D,bcoz MED is a optional
> > > > Non-transitive attribute,which never passed to EBGP peers.
> > > >
> > > >
> > > > Thanks
> > > > Mohamed.
> > > >
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > > > Behalf
> >
> > > > Of Sergio Jimenez Arguedas
> > > > Sent: Wednesday, April 28, 2004 2:29 AM
> > > > To: ccielab@groupstudy.com
> > > > Subject: BGP MED Scenario!!!
> > > >
> > > >
> > > > Hi Group,
> > > >
> > > > I have a question about BGP MED, the scenario is the following:
> > > >
> > > >
> > > >
> > > > --------------EB GP----------------------R4
> > > > OSPF |
> > > > |ibgp
> > > > NETA
> > > > ----------R1------------------------------R2------------EBGP----
> > > > --
> > > > --
> > > > --
> > > > --
> > > > -----
> > > > -----R3-------------EBGP-----------------R5
> > > >
> > > >
> > > > R1 Tx NETA to R2 by OSPF and R2 Tx NetA to R3/R4 by EBGP. R3 and
> > > > R4 Rx
> > >
> > > > NETA with the IGP (OSPF) metric. When R3 Tx the route R5, R5 Rx
> > > > the route with the metric 0. I understood it, but I have the
> > > > following
> > > > question:
> > > >
> > > >
> > > > If I apply a route-map from R3 to R5 with set metric-type
> > > > internal.......This would cause BGP routes to carry the internal
> > > > IGP
> >
> > > > metric as the BGP MED?
> > > >
> > > > R3/R4 carried the IGP metric without a route-map in R2.
> > > >
> > > >
> > > >
> > > > Could you help me, please?
> > > >
> > > >
> > > > Reference: HALABI Pag_340
> > > >
> > > >
> > > >
> > > > Rgds,
> > > >
> > > >
> > > > Sergio Jiminez A.
> > > >
> > > > ________________________________________________________________
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