ospfd: Implement forwarding-address-self command #20077
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Signed-off-by: Donatas Abraitis <[email protected]>
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This command will be used to force external LSAs to be generated with the
Forwarding Address to be set to self to allow receiving routers sending the
traffic directly to the ASBR router instead of relying on the FD.
The use case is for ECMP if we receive an external LSA with the identical FD.
So in this case only a single entry will be installed into the RIB.
r3# show ip ospf database external
OSPF Router with ID (172.16.0.3)
AS External Link States
LS age: 66
Options: 0x2 : *|-|-|-|-|-|E|-
LS Flags: 0x6
LS Type: AS-external-LSA
Link State ID: 172.16.10.0 (External Network Number)
Advertising Router: 172.16.0.1
LS Seq Number: 80000001
Checksum: 0x1f1b
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 0.0.0.0
External Route Tag: 0
LS age: 63
Options: 0x2 : *|-|-|-|-|-|E|-
LS Flags: 0x6
LS Type: AS-external-LSA
Link State ID: 172.16.10.0 (External Network Number)
Advertising Router: 172.16.0.2
LS Seq Number: 80000001
Checksum: 0x1920
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 0.0.0.0
External Route Tag: 0
r3# show ip route 172.16.10.0/24
Routing entry for 172.16.10.0/24
Known via "ospf", distance 110, metric 20, best
Last update 00:00:25 ago
Flags: Selected
Status: Installed
* 172.16.0.1, via r3-eth0, weight 1
* 172.16.0.2, via r3-eth0, weight 1
Without this feature we have
============================
r3# show ip ospf database external
OSPF Router with ID (172.16.0.3)
AS External Link States
LS age: 68
Options: 0x2 : *|-|-|-|-|-|E|-
LS Flags: 0x6
LS Type: AS-external-LSA
Link State ID: 172.16.10.0 (External Network Number)
Advertising Router: 172.16.0.1
LS Seq Number: 80000001
Checksum: 0xd79b
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 172.16.0.10
External Route Tag: 0
LS age: 65
Options: 0x2 : *|-|-|-|-|-|E|-
LS Flags: 0x6
LS Type: AS-external-LSA
Link State ID: 172.16.10.0 (External Network Number)
Advertising Router: 172.16.0.2
LS Seq Number: 80000001
Checksum: 0xd1a0
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 172.16.0.10
External Route Tag: 0
r3# show ip route
Codes: K - kernel route, C - connected, L - local, S - static,
R - RIP, O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
F - PBR, f - OpenFabric, t - Table-Direct,
> - selected route, * - FIB route, q - queued, r - rejected, b - backup
t - trapped, o - offload failure
IPv4 unicast VRF default:
O 172.16.0.0/24 [110/10] is directly connected, r3-eth0, weight 1, 00:01:05
C>* 172.16.0.0/24 is directly connected, r3-eth0, weight 1, 00:01:05
L>* 172.16.0.3/32 is directly connected, r3-eth0, weight 1, 00:01:05
O>* 172.16.10.0/24 [110/20] via 172.16.0.10, r3-eth0, weight 1, 00:00:19
Signed-off-by: Donatas Abraitis <[email protected]>
Signed-off-by: Donatas Abraitis <[email protected]>
ton31337
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r1# show ip ospf json
{
...
"forwardingAddressSelf":true,
...
}
or
r1# show ip ospf
OSPF Routing Process, Router ID: 240.0.0.100
...
Forwarding address is set to self for external LSAs <<<<<<
...
Signed-off-by: Donatas Abraitis <[email protected]>
Jafaral
approved these changes
Nov 21, 2025
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