Can non-recursive BGP route be used to determine next-hop for recursive BGP route?
In BGP recursive scenario, the recursive route is taking an unexpected next-hop. Here is the routing table:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
B 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS, 2d18h20m
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 10.10.10.1), 1d1h10m
The next-hop of the recursive route should be the second route in the table which is another BGP route. However, it's taking the default route on top.
When adding a static route which is exactly the same as the second BGP route, next-hop is determined correctly:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
S 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 172.80.80.1), 1d1h10m
Is this an expected behavior?
routing router bgp next-hop
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In BGP recursive scenario, the recursive route is taking an unexpected next-hop. Here is the routing table:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
B 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS, 2d18h20m
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 10.10.10.1), 1d1h10m
The next-hop of the recursive route should be the second route in the table which is another BGP route. However, it's taking the default route on top.
When adding a static route which is exactly the same as the second BGP route, next-hop is determined correctly:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
S 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 172.80.80.1), 1d1h10m
Is this an expected behavior?
routing router bgp next-hop
asked yesterday
onlyforthisonlyforthis
1313
New contributor
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
In BGP recursive scenario, the recursive route is taking an unexpected next-hop. Here is the routing table:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
B 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS, 2d18h20m
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 10.10.10.1), 1d1h10m
The next-hop of the recursive route should be the second route in the table which is another BGP route. However, it's taking the default route on top.
When adding a static route which is exactly the same as the second BGP route, next-hop is determined correctly:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
S 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 172.80.80.1), 1d1h10m
Is this an expected behavior?
routing router bgp next-hop
asked yesterday
onlyforthisonlyforthis
1313
New contributor
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
In BGP recursive scenario, the recursive route is taking an unexpected next-hop. Here is the routing table:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
B 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS, 2d18h20m
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 10.10.10.1), 1d1h10m
The next-hop of the recursive route should be the second route in the table which is another BGP route. However, it's taking the default route on top.
When adding a static route which is exactly the same as the second BGP route, next-hop is determined correctly:
S* 0.0.0.0/0 [10/0] via 10.10.10.1, wan
S 172.16.5.0/24 [20/0] via 172.80.80.1, MPLS
B 192.168.250.0/24 [20/0] via 172.16.5.1 (recursive via 172.80.80.1), 1d1h10m
Is this an expected behavior?
routing router bgp next-hop
routing router bgp next-hop
asked yesterday
onlyforthisonlyforthis
1313
New contributor
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked yesterday
onlyforthisonlyforthis
1313
New contributor
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited yesterday
onlyforthis
asked yesterday
onlyforthisonlyforthis
1313
New contributor
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked yesterday
onlyforthisonlyforthis
1313
asked yesterday
onlyforthisonlyforthis
1313
1313
New contributor
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
onlyforthis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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1 Answer
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IOS will not use another BGP route for recursive lookup for a BGP route. This is somewhat hinted at in the "Why Routers Ignore Paths" section of the "BGP Best Path Selection Algorithm" documentation:
[Routers ignore] paths for which the NEXT_HOP is inaccessible.
Be sure that there is an Interior Gateway Protocol (IGP) route to the NEXT_HOP that is associated with the path.
So yes, this is expected behavior on IOS. Other routing platforms may behave differently. There is also an article describing further how the lookup works.
answered yesterday
SebastianSebastian
5,91822251
Thanks. This was useful. I wonder if this is a standard BGP behavior or vendor specific.
– onlyforthis
yesterday
@onlyforthis: I suspect it's mostly standard. For example, RouterOS requires the nexthop scope to be lower than the route's own.
– grawity
yesterday
@onlyforthis It depends on the vendor, Juniper can use BGP routes for recursive lookup. If this answers you question please accept it as answer.
– Sebastian
yesterday
add a comment |
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1 Answer
1
active
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1 Answer
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active
oldest
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IOS will not use another BGP route for recursive lookup for a BGP route. This is somewhat hinted at in the "Why Routers Ignore Paths" section of the "BGP Best Path Selection Algorithm" documentation:
[Routers ignore] paths for which the NEXT_HOP is inaccessible.
Be sure that there is an Interior Gateway Protocol (IGP) route to the NEXT_HOP that is associated with the path.
So yes, this is expected behavior on IOS. Other routing platforms may behave differently. There is also an article describing further how the lookup works.
answered yesterday
SebastianSebastian
5,91822251
Thanks. This was useful. I wonder if this is a standard BGP behavior or vendor specific.
– onlyforthis
yesterday
@onlyforthis: I suspect it's mostly standard. For example, RouterOS requires the nexthop scope to be lower than the route's own.
– grawity
yesterday
@onlyforthis It depends on the vendor, Juniper can use BGP routes for recursive lookup. If this answers you question please accept it as answer.
– Sebastian
yesterday
add a comment |
IOS will not use another BGP route for recursive lookup for a BGP route. This is somewhat hinted at in the "Why Routers Ignore Paths" section of the "BGP Best Path Selection Algorithm" documentation:
[Routers ignore] paths for which the NEXT_HOP is inaccessible.
Be sure that there is an Interior Gateway Protocol (IGP) route to the NEXT_HOP that is associated with the path.
So yes, this is expected behavior on IOS. Other routing platforms may behave differently. There is also an article describing further how the lookup works.
answered yesterday
SebastianSebastian
5,91822251
Thanks. This was useful. I wonder if this is a standard BGP behavior or vendor specific.
– onlyforthis
yesterday
@onlyforthis: I suspect it's mostly standard. For example, RouterOS requires the nexthop scope to be lower than the route's own.
– grawity
yesterday
@onlyforthis It depends on the vendor, Juniper can use BGP routes for recursive lookup. If this answers you question please accept it as answer.
– Sebastian
yesterday
add a comment |
IOS will not use another BGP route for recursive lookup for a BGP route. This is somewhat hinted at in the "Why Routers Ignore Paths" section of the "BGP Best Path Selection Algorithm" documentation:
[Routers ignore] paths for which the NEXT_HOP is inaccessible.
Be sure that there is an Interior Gateway Protocol (IGP) route to the NEXT_HOP that is associated with the path.
So yes, this is expected behavior on IOS. Other routing platforms may behave differently. There is also an article describing further how the lookup works.
answered yesterday
SebastianSebastian
5,91822251
IOS will not use another BGP route for recursive lookup for a BGP route. This is somewhat hinted at in the "Why Routers Ignore Paths" section of the "BGP Best Path Selection Algorithm" documentation:
[Routers ignore] paths for which the NEXT_HOP is inaccessible.
Be sure that there is an Interior Gateway Protocol (IGP) route to the NEXT_HOP that is associated with the path.
So yes, this is expected behavior on IOS. Other routing platforms may behave differently. There is also an article describing further how the lookup works.
answered yesterday
SebastianSebastian
5,91822251
answered yesterday
SebastianSebastian
5,91822251
answered yesterday
SebastianSebastian
5,91822251
answered yesterday
SebastianSebastian
5,91822251
5,91822251
Thanks. This was useful. I wonder if this is a standard BGP behavior or vendor specific.
– onlyforthis
yesterday
@onlyforthis: I suspect it's mostly standard. For example, RouterOS requires the nexthop scope to be lower than the route's own.
– grawity
yesterday
@onlyforthis It depends on the vendor, Juniper can use BGP routes for recursive lookup. If this answers you question please accept it as answer.
– Sebastian
yesterday
add a comment |
Thanks. This was useful. I wonder if this is a standard BGP behavior or vendor specific.
– onlyforthis
yesterday
@onlyforthis: I suspect it's mostly standard. For example, RouterOS requires the nexthop scope to be lower than the route's own.
– grawity
yesterday
@onlyforthis It depends on the vendor, Juniper can use BGP routes for recursive lookup. If this answers you question please accept it as answer.
– Sebastian
yesterday
Thanks. This was useful. I wonder if this is a standard BGP behavior or vendor specific.
– onlyforthis
yesterday
Thanks. This was useful. I wonder if this is a standard BGP behavior or vendor specific.
– onlyforthis
yesterday
@onlyforthis: I suspect it's mostly standard. For example, RouterOS requires the nexthop scope to be lower than the route's own.
– grawity
yesterday
@onlyforthis: I suspect it's mostly standard. For example, RouterOS requires the nexthop scope to be lower than the route's own.
– grawity
yesterday
@onlyforthis It depends on the vendor, Juniper can use BGP routes for recursive lookup. If this answers you question please accept it as answer.
– Sebastian
yesterday
@onlyforthis It depends on the vendor, Juniper can use BGP routes for recursive lookup. If this answers you question please accept it as answer.
– Sebastian
yesterday
add a comment |
onlyforthis is a new contributor. Be nice, and check out our Code of Conduct.
onlyforthis is a new contributor. Be nice, and check out our Code of Conduct.
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