bgp load balance

densma

i asked this a while on group study but didnt get any response.
when ask to do bgp load balance is it necessary to export policy into forwarding table for multipath load balancing.

what i observed, (R3-T1/T2 case study example) load balance with multipath only install one prefix in forwarding table. unless you export policy to load balance in fowarding table.

the other way around. (R4-C1 case study example) load balance with multihop automatically handle forwarding table load balance.

do you know with multipath load balance if it require especially in JNCIP lab to export policy to fowarding table?

here EBGP R3-T1-T2 example


root@R3# edit protocols bgp group t1-t2

[edit protocols bgp group t1-t2]
root@R3# show
multipath;
neighbor 172.16.0.18 {
description T2;
peer-as 65222;
}
neighbor 172.16.0.14 {
description T1;
peer-as 65222;
}

[edit protocols bgp group t1-t2]
root@R3# run show bgp summary
Groups: 3 Peers: 6 Down peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0 50 45 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Damped...
172.16.0.14 65222 33 23 0 0 8:32 13/13/0 0/0/0
172.16.0.18 65222 36 26 0 0 9:14 13/13/0 0/0/0
10.0.3.4 65412 1232 1471 0 0 11:04:50 13/16/0 0/0/0
10.0.3.5 65412 1228 1465 0 0 11:02:49 3/4/0 0/0/0
10.0.6.1 65412 1260 1525 0 0 11:03:02 1/2/0 0/0/0
10.0.6.2 65412 1233 1522 0 0 11:02:58 2/2/0 0/0/0



[edit protocols bgp group t1-t2]
root@R3# run show route forwarding-table destination 130.130.1/24
Routing table: inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
130.130.1.0/24 user 0 172.16.0.18 ucst 479 14 fxp4.0

Routing table: __juniper_private1__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 83 1

Routing table: __juniper_private2__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 139 1

[edit protocols bgp group t1-t2]
root@R3# exit

[edit]
root@R3# edit policy-options policy-statement lb

[edit policy-options policy-statement lb]

[edit policy-options policy-statement lb]
root@R3# set from neighbor 172.16.0.14

[edit policy-options policy-statement lb]
root@R3# set from neighbor 172.16.0.18

[edit policy-options policy-statement lb]


[edit policy-options policy-statement lb]
root@R3# set then load-balance per-packet

[edit policy-options policy-statement lb]
root@R3# show
from neighbor [ 172.16.0.14 172.16.0.18 ];
then {
load-balance per-packet;
}

[edit policy-options policy-statement lb]
root@R3# exit

[edit]
root@R3# edit routing-options forwarding-table

[edit routing-options forwarding-table]
root@R3# set export lb

[edit routing-options forwarding-table]
root@R3# exit

[edit]
root@R3# run show route forwarding-table destination 130.130.1/24
Routing table: inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
130.130.1.0/24 user 0 172.16.0.18 ucst 479 14 fxp4.0

Routing table: __juniper_private1__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 83 1

Routing table: __juniper_private2__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 139 1

[edit]
root@R3# commit
commit complete

[edit]
root@R3# run show route forwarding-table destination 130.130.1/24
Routing table: inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
130.130.1.0/24 user 0 ulst 131076 15
172.16.0.14 ucst 480 3 fxp3.0
172.16.0.18 ucst 479 4 fxp4.0

Routing table: __juniper_private1__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 83 1

Routing table: __juniper_private2__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 139 1

[edit]
root@R3#

HERE'S R4-C1 MULTIHOP EXAMPLE

root@R4# edit protocols bgp group c1

[edit protocols bgp group c1]
root@R4# show
local-address 10.0.3.4;
neighbor 200.200.0.1 {
description c1;
multihop;
authentication-key "$9$.fQnEhrlMX"; ## SECRET-DATA
peer-as 65010;
}

[edit protocols bgp group c1]
root@R4# exit

[edit]
root@R4# run show route 200.200.1/24

inet.0: 61 destinations, 64 routes (61 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

200.200.1.0/24 *[BGP/170] 00:06:21, localpref 100, from 200.200.0.1
AS path: 65010 I
> to 172.16.0.6 via fxp3.0
to 172.16.0.10 via fxp4.0


root@R4# run show route forwarding-table destination 200.200.1/24
Routing table: inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
200.200.1.0/24 user 0 indr 131077 16
ulst 131076 2
172.16.0.6 ucst 475 6 fxp3.0
172.16.0.10 ucst 474 2 fxp4.0

Routing table: __juniper_private1__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 83 1

Routing table: __juniper_private2__.inet
Internet:
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 139 1

[edit]
root@R4#

Aldur

densma wrote: »

i asked this a while on group study but didnt get any response.
when ask to do bgp load balance is it necessary to export policy into forwarding table for multipath load balancing.

...

do you know with multipath load balance if it require especially in JNCIP lab to export policy to fowarding table?

Just simply using multipath will allow 2 bgp routes to be activite in the route table at the same time, effectively skipping steps 9 and 10 in the bgp selection algorithm. However this does nothing for load balancing since only one route is installed in the forwarding table.

You are correct in that to really do load balancing you need to have a export policy in the forwarding table that tells it to do this.

Do you need to know this for the test? Well I can't say much about that without breaking NDA. But if you feel that you need to apply a load balancing export policy to the forwarding table I don't think that would cause any harm, even if they don't ask for it. Either way it's a simple matter so I wouldn't stress about it to much.