I have a setup as in the attached drawing. I can see that the bird ABR node
(R2) sets the E-bit and the B-bit in the router LSA. The B-bit seems correct as
it is the ABR, but it is not an ASBR.
Below is a tcpdump captured on R1
Frame 11347: 124 bytes on wire (992 bits), 124 bytes captured (992 bits)
Linux cooked capture v2
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4, Src: 10.210.138.69, Dst: 224.0.0.5
Open Shortest Path First
OSPF Header
Version: 2
Message Type: LS Update (4)
Packet Length: 76
Source OSPF Router: 10.210.138.69
Area ID: 0.0.0.0 (Backbone)
Checksum: 0x9d61 [correct]
Auth Type: Null (0)
Auth Data (none): 0000000000000000
LS Update Packet
Number of LSAs: 1
LSA-type 1 (Router-LSA), len 48
.000 0000 0000 0001 = LS Age (seconds): 1
0... .... .... .... = Do Not Age Flag: 0
Options: 0x42, O, (E) External Routing
0... .... = DN: Not set
.1.. .... = O: Set
..0. .... = (DC) Demand Circuits: Not supported
...0 .... = (L) LLS Data block: Not Present
.... 0... = (N) NSSA: Not supported
.... .0.. = (MC) Multicast: Not capable
.... ..1. = (E) External Routing: Capable
.... ...0 = (MT) Multi-Topology Routing: No
LS Type: Router-LSA (1)
Link State ID: 10.210.138.69
Advertising Router: 10.210.138.69
Sequence Number: 0x80000075
Checksum: 0x180f
Length: 48
Flags: 0x03, (E) AS boundary router, (B) Area border router
0... .... = (H) flag: No
...0 .... = (N) flag: No
.... 0... = (W) Wild-card multicast receiver: No
.... .0.. = (V) Virtual link endpoint: No
.... ..1. = (E) AS boundary router: Yes
.... ...1 = (B) Area border router: Yes
Number of Links: 2
Type: Stub ID: 10.210.138.69 Data: 255.255.255.255 Metric: 0
Type: PTP ID: 10.210.138.66 Data: 10.210.138.69 Metric: 10
The Cisco router sees these bird routers as ASBR routers as well
R3-Cisco>show ip ospf border-routers
OSPF Router with ID (10.210.138.65) (Process ID 1)
Base Topology (MTID 0)
Internal Router Routing Table
Codes: i - Intra-area route, I - Inter-area route
i 10.210.138.66 [1] via 10.210.138.66, GigabitEthernet0/0/1, ASBR, Area
0.0.0.0, SPF 77
i 10.210.138.69 [11] via 10.210.138.66, GigabitEthernet0/0/1, ABR/ASBR, Area
0.0.0.0, SPF 77
I 10.210.138.73 [21] via 10.210.138.66, GigabitEthernet0/0/1, ASBR, Area
0.0.0.0, SPF 77
R3-Cisco>
R3-Cisco>show ip ospf database
OSPF Router with ID (10.210.138.65) (Process ID 1)
Router Link States (Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum Link count
10.210.138.65 10.210.138.65 870 0x800000DE 0x0091B0 2
10.210.138.66 10.210.138.66 828 0x800000AC 0x00DBB2 3
10.210.138.69 10.210.138.69 828 0x8000009F 0x00C339 2
Net Link States (Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum
10.210.138.65 10.210.138.65 870 0x80000035 0x003F26
Summary Net Link States (Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum
10.210.138.73 10.210.138.69 591 0x8000002D 0x002465
Summary ASB Link States (Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum
10.210.138.73 10.210.138.69 591 0x8000002D 0x001672
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 10.210.138.65 1650 0x80000034 0x004EA1 1
R3-Cisco>
