Displayed Routes in "sh ipr" different than expected based on LSDB

[Timothy_Corcora]

Issue:

Why does sh IPR treat destination networks differently even though at first glance they should be treated the same?



Referring to this diagram: Mah-670-1 and Mah-670-2 are routers serving as the gateway between a building and the larger campus network. Dug-agg-1 and Dug-agg-2 are the aggregation routers that connect them to the OSPF area (0.0.3.2) that they all belong to.

Mah-670-1 has an OSPF P2P link with Dug-agg-1 and with Mah-670-2.

Mah 670-2 has an OSPF P2P link with Dug-agg-2 and with Mah-670-1.

Dug-agg1 and Dug-agg-2 have an OSPF P2P link to each other as well as P2P links to the larger campus network. All P2P and passive VLANs are in the same VR.

The sh ipr for mah-670-1 shows :

#or 10.112.1.0/24 10.3.11.157 12 UG-D---um--f- CA-P2P-Dagg1 4d:22h:16m:17s

#or 10.112.1.0/24 10.3.11.214 12 UG-D---um--f- ca-p2p-Mah-int 4d:22h:16m:17s

#or 10.113.1.0/24 10.3.11.157 10 UG-D---um--c- CA-P2P-Dagg1 4d:22h:16m:17s

#or 10.114.1.0/24 10.3.11.157 10 UG-D---um--c- CA-P2P-Dagg1 4d:22h:16m:17s



All of these routes are #or

Why then, does the 10.112.1.0/24 show two routes in the routing table (one through the Agg, one through the bld partner)

While the 10.113 and 10.114 show only one route (through the agg)?



Please note that both routes appear in the lsdb summary for each network.



Sh ospf lsdb

10.112.1.0 10.56.1.4 0x800009ed 117 0xcccd

10.112.1.0 10.56.2.4 0x800009ef 1091 0xadeb

10.113.1.0 10.56.1.4 0x800030d0 1437 0x7120

10.113.1.0 10.56.2.4 0x80004add 1571 0x 267

10.114.1.0 10.56.1.4 0x800025ed 1437 0x4c32

10.114.1.0 10.56.2.4 0x800025f4 1571 0x373f



The LSDB tells the router about both paths to each network.

The IPR table chooses to show both paths for 112.1, But only one path for 113.1 and 114.1

Why?

[Erik_Auerswald]

Hi,

my original answer to the question was lost in the platform troubles. 😞

The OSPF LSDB show differences for the prefixes 10.112.1.0/24 and 10.113.1.0/24:

• both are known via type 3 LSA
• the metrics from the two ABRs are different for 10.112.1.0/24, but the same for 10.113.1.0/24
• the cost to the two ABRs should be different because of the square topology, which is confirmed by 10.112.1.0/24 showing two least cost paths and ECMP

Thus only 10.112.1.0/24 is known via two least cost paths that can be used for ECMP, the prefix 10.113.1.0/24 has but one least cost path, so no ECMP is possible.

Since 10.113.1.0/24 and 10.114.1.0/24 are compressed (flag c), i.e. omitted from the FIB, because a less specific prefix including both 10.113.10/24 and 10.114.1.0/24 has the exact same next hop(s), prefix 10.112.1.0/24 seems to be the outlier here.

Thanks,
Erik

[Timothy_Corcora]

This is the nub of my question. OSPF seems to see 10.112.1.0 and 10.113.1.0 in the same way but show iproute treats them differently.

(vr VR-Campus) Mah-670-1.10 # sh ipr 10.112.1.0/24
Ori Destination Gateway Mtr Flags VLAN Duration
#or 10.112.1.0/24 10.3.11.157 12 UG-D---um--f- CA-P2P-Dagg1 8d:0h:41m:33s
#or 10.112.1.0/24 10.3.11.214 12 UG-D---um--f- ca-p2p-Mah-int 8d:0h:41m:33s

(mo) MOSPF (o) OSPF, (o1) OSPFExt1, (o2) OSPFExt2,
(oa) OSPFIntra, (oe) OSPFAsExt, (or) OSPFInter, (pd) PIM-DM, (ps) PIM-SM,
(r) RIP, (ra) RtAdvrt, (s) Static, (sv) SLB_VIP, (un) UnKnown,
(*) Preferred unicast route (@) Preferred multicast route,
(#) Preferred unicast and multicast route.

Flags: (b) BFD protection requested, (B) BlackHole, (c) Compressed, (D) Dynamic,
(f) Provided to FIB, (G) Gateway, (H) Host Route, (l) Calculated LDP LSP,
(L) Matching LDP LSP, (m) Multicast, (p) BFD protection active, (P) LPM-routing,
(R) Modified, (s) Static LSP, (S) Static, (t) Calculated RSVP-TE LSP,
(T) Matching RSVP-TE LSP, (u) Unicast, (U) Up, (3) L3VPN Route.

MPLS Label: (S) Bottom of Label Stack
Mask distribution:
2 routes at length 24

Route Origin distribution:
2 routes from OSPFInter

Total number of routes = 2
Total number of compressed routes = 0

(vr VR-Campus) Mah-670-1.11 # sh ipr 10.113.1.0/24
Ori Destination Gateway Mtr Flags VLAN Duration
#or 10.113.1.0/24 10.3.11.157 10 UG-D---um--c- CA-P2P-Dagg1 8d:0h:41m:40s

(mo) MOSPF (o) OSPF, (o1) OSPFExt1, (o2) OSPFExt2,
(oa) OSPFIntra, (oe) OSPFAsExt, (or) OSPFInter, (pd) PIM-DM, (ps) PIM-SM,
(r) RIP, (ra) RtAdvrt, (s) Static, (sv) SLB_VIP, (un) UnKnown,
(*) Preferred unicast route (@) Preferred multicast route,
(#) Preferred unicast and multicast route.

Flags: (b) BFD protection requested, (B) BlackHole, (c) Compressed, (D) Dynamic,
(f) Provided to FIB, (G) Gateway, (H) Host Route, (l) Calculated LDP LSP,
(L) Matching LDP LSP, (m) Multicast, (p) BFD protection active, (P) LPM-routing,
(R) Modified, (s) Static LSP, (S) Static, (t) Calculated RSVP-TE LSP,
(T) Matching RSVP-TE LSP, (u) Unicast, (U) Up, (3) L3VPN Route.

MPLS Label: (S) Bottom of Label Stack
Mask distribution:
1 routes at length 24

Route Origin distribution:
1 routes from OSPFInter

Total number of routes = 1
Total number of compressed routes = 1

(vr VR-Campus) Mah-670-1.12 #

[Timothy_Corcora]

Understood. Here we go:

(vr VR-Campus) Mah-670-1.3 # sh ospf lsdb det lsid 10.112.1.0

LSAs for Area: 0.0.3.2

LSA Type: Summary Network
Link State Id: 10.112.1.0 (Destination Network Ip Address)
Options: None
Advertising Router: 10.56.1.4
Sequence number: 0x80000a81
Checksum: 0xa263
Age: 392
Length: 28
Receive Interface: None
Network Mask: 255.255.255.0
Cost (TOS 0 Metric): 10

LSA Type: Summary Network
Link State Id: 10.112.1.0 (Destination Network Ip Address)
Options: None
Advertising Router: 10.56.2.4
Sequence number: 0x80000a83
Checksum: 0x8381
Age: 1631
Length: 28
Receive Interface: None
Network Mask: 255.255.255.0
Cost (TOS 0 Metric): 8

(vr VR-Campus) Mah-670-1.4 # sh ospf lsdb det lsid 10.113.1.0

LSAs for Area: 0.0.3.2

LSA Type: Summary Network
Link State Id: 10.113.1.0 (Destination Network Ip Address)
Options: None
Advertising Router: 10.56.1.4
Sequence number: 0x80003164
Checksum: 0x47b5
Age: 1762
Length: 28
Receive Interface: None
Network Mask: 255.255.255.0
Cost (TOS 0 Metric): 8

LSA Type: Summary Network
Link State Id: 10.113.1.0 (Destination Network Ip Address)
Options: None
Advertising Router: 10.56.2.4
Sequence number: 0x80004b72
Checksum: 0xd5fd
Age: 361
Length: 28
Receive Interface: None
Network Mask: 255.255.255.0
Cost (TOS 0 Metric): 8

(vr VR-Campus) Mah-670-1.5 #

[Erik_Auerswald]

Thanks, but I need the detailed output for just the LSAs in question. This should be possible to get using the following commands (untested, so you might need to tweak them):
show ospf lsdb detail lsid 10.112.1.0
show ospf lsdb detail lsid 10.113.1.0I want to check if those are of different type, e.g. one type 3 and the other type 5.

[Timothy_Corcora]

Erik,
I edited the displays to show the pertinent information for the sake of brevity. the full output is included below:
Mah-670-1.1 # vir vr-ca
(vr VR-Campus) Mah-670-1.2 # sh ospf lsdb

AS External LSAs
Link State ID Adv Router Seq# Age Chksum Tag
-------------------------------------------------------------
0.0.0.0 10.56.240.4 0x80004d64 857 0x39a5 0
10.12.4.0 10.255.230.4 0x80000904 1559 0x1358 0
10.12.7.0 10.255.230.4 0x80000904 1559 0xf176 0
10.12.9.0 10.255.230.4 0x80000904 1559 0xdb8a 0
10.12.10.0 10.255.230.4 0x80000904 1559 0xd094 0
10.12.13.0 10.255.230.4 0x80000904 1559 0xafb2 0
10.12.14.0 10.255.230.4 0x80000904 1559 0xa4bc 0
10.12.55.0 10.255.229.4 0x8000aa93 967 0x705a 0
10.12.55.0 10.255.230.4 0x80000904 1559 0x6d8d 0
10.12.65.0 10.255.230.4 0x800003bf 1109 0x c6c 0
10.27.60.0 10.255.242.4 0x80004e92 990 0x138b 0
10.91.0.0 10.92.241.4 0x80005a19 1057 0x7082 0
10.97.1.0 10.255.241.4 0x80002308 1542 0xa190 0
10.99.9.0 10.255.229.4 0x80002d64 1538 0x9ded 0
129.63.40.0 10.255.242.4 0x8001cf66 990 0x2dba 0
129.63.41.0 10.255.242.4 0x8001cf66 990 0x22c4 0
129.63.42.0 10.255.8.4 0x8000040b 337 0x9b5e 0
129.63.43.0 10.255.8.4 0x8000040b 337 0x9068 0
172.31.146.0 10.11.240.4 0x800078bf 1366 0x1c10 0
172.31.146.0 10.11.241.4 0x800078bf 1389 0x3fe8 0
192.168.1.0 10.255.175.4 0x80007972 1140 0xfedc 0
192.168.125.0 10.255.8.4 0x80013ae1 938 0x8ea1 0

Router LSAs for area 0.0.3.2
Link State ID Adv Router Seq# Age Chksum #Links
-------------------------------------------------------------
10.33.240.4 10.33.240.4 0x80000181 512 0xbe7f 8
10.33.241.4 10.33.241.4 0x80000182 519 0x af7 8
10.34.240.4 10.34.240.4 0x8000c4dc 1090 0x89b2 7
10.34.241.4 10.34.241.4 0x8000c4dd 1063 0x640e 6
10.38.240.4 10.38.240.4 0x800069ff 1063 0xbef2 12
10.38.241.4 10.38.241.4 0x80006a37 1385 0xee5f 12
10.44.240.4 10.44.240.4 0x80000339 1565 0x54c7 6
10.44.241.4 10.44.241.4 0x80000339 1603 0x88fd 7
10.56.1.4 10.56.1.4 0x8000dbd0 152 0x13eb 15
10.56.2.4 10.56.2.4 0x8000e3b8 847 0x59d9 13
10.56.220.4 10.56.220.4 0x80003e7b 630 0xa971 12
10.56.221.4 10.56.221.4 0x80003e6e 1330 0xa945 12
10.95.240.4 10.95.240.4 0x8000492e 615 0xeac1 8
10.95.241.4 10.95.241.4 0x8000492c 1659 0xec06 6
10.255.59.4 10.255.59.4 0x8000daeb 529 0x5906 18
10.255.60.4 10.255.60.4 0x8000e412 1271 0xc338 18

Summary LSAs for area 0.0.3.2
Link State ID Adv Router Seq# Age Chksum
-------------------------------------------------------------
10.3.0.128 10.56.1.4 0x80000f53 753 0x41d8
10.3.0.128 10.56.2.4 0x80000f57 608 0x1ef8
10.3.0.152 10.56.1.4 0x80003163 663 0x3da0
10.3.0.152 10.56.2.4 0x8000316f 1058 0x5a70
10.3.0.176 10.56.1.4 0x80003162 663 0x764c
10.3.0.176 10.56.2.4 0x80008530 1058 0xd6c8
10.3.0.200 10.56.1.4 0x80000f60 513 0xefde
10.3.0.200 10.56.2.4 0x80000f60 399 0xfcce
10.3.0.224 10.56.1.4 0x80003162 663 0xa8e7
10.3.0.224 10.56.2.4 0x8000316d 1058 0x4f3b
10.3.0.248 10.56.1.4 0x80000f5d 213 0x2877
10.3.0.248 10.56.2.4 0x80000f62 69 0x 398
10.3.1.4 10.56.1.4 0x80003161 663 0x1859
10.3.1.4 10.56.2.4 0x8000316d 1058 0xf86b
10.3.1.32 10.56.1.4 0x8000850a 663 0xb0a7
10.3.1.32 10.56.2.4 0x8000852c 1058 0x79b9
10.3.1.56 10.56.1.4 0x80003163 663 0xf547
10.3.1.56 10.56.2.4 0x8000316f 1058 0xfe2d
10.3.1.80 10.56.1.4 0x8000bd7c 663 0x413c
10.3.1.80 10.56.2.4 0x8000bda3 1058 0xff53
10.3.1.104 10.56.1.4 0x80000628 1774 0x2051
10.3.1.104 10.56.2.4 0x8000062a 968 0x2943
10.3.1.132 10.56.1.4 0x80003162 663 0x11de
10.3.1.132 10.56.2.4 0x8000bda1 1058 0xf927
10.3.1.156 10.56.1.4 0x80003162 663 0x34a1
10.3.1.156 10.56.2.4 0x8000316d 1058 0x 3c8
10.3.1.180 10.56.1.4 0x80003163 663 0x417b
10.3.1.180 10.56.2.4 0x8000d99c 1058 0xa538
10.3.1.204 10.56.1.4 0x80003164 784 0x4e55
10.3.1.204 10.56.2.4 0x8000bda0 1058 0x15c6
10.3.1.228 10.56.1.4 0x800004b4 1144 0x4424
10.3.1.228 10.56.2.4 0x800004b5 1508 0x2741
10.3.2.0 10.56.1.4 0x80003163 663 0x452b
10.3.2.0 10.56.2.4 0x8000bd9f 1058 0x c9c
10.3.2.36 10.56.1.4 0x8000d96b 663 0xa9f5
10.3.2.36 10.56.2.4 0x8000bda4 1058 0xc0ba
10.3.2.84 10.56.1.4 0x80003163 663 0x e0c
10.3.2.84 10.56.2.4 0x8000d99c 1058 0x5ede
10.3.2.108 10.56.1.4 0x80003162 663 0x bf9
10.3.2.108 10.56.2.4 0x8000bda4 1058 0xd95b
10.3.2.204 10.56.1.4 0x80003162 663 0x475d
10.3.2.204 10.56.2.4 0x80004b27 1058 0x7c46
10.3.2.228 10.56.1.4 0x80000f5f 513 0xd6d8
10.3.2.228 10.56.2.4 0x80000f65 429 0xc3e4
10.3.3.64 10.56.1.4 0x80003162 663 0xcd60
10.3.3.64 10.56.2.4 0x800058de 1058 0x5831
10.3.3.80 10.56.1.4 0x80000f84 1414 0x4fce
10.3.3.80 10.56.2.4 0x80000f8c 1328 0x38dc
10.3.3.100 10.56.1.4 0x80000f85 3 0x709a
10.3.3.100 10.56.2.4 0x8000852f 1748 0xc621
10.3.3.124 10.56.1.4 0x80003163 1444 0x717f
10.3.3.124 10.56.2.4 0x80000f88 1328 0x727c
10.3.3.148 10.56.1.4 0x80003162 663 0x6e6d
10.3.3.148 10.56.2.4 0x80004b6e 1058 0x159d
10.3.3.176 10.56.1.4 0x80000f61 333 0xd10f
10.3.3.176 10.56.2.4 0x80000f69 189 0xba1d
10.3.3.196 10.56.1.4 0x80000f61 1744 0xf4d9
10.3.3.196 10.56.2.4 0x80000f65 1598 0xf9cd
10.3.3.220 10.56.1.4 0x80000f61 333 0x189c
10.3.3.220 10.56.2.4 0x80000f66 219 0xf2bd
10.3.4.64 10.56.1.4 0x80003162 663 0xae80
10.3.4.64 10.56.2.4 0x8000b715 1058 0xc230
10.3.4.88 10.56.1.4 0x80003162 663 0xd143
10.3.4.88 10.56.2.4 0x8000b748 1058 0x5752
10.3.4.112 10.56.1.4 0x80003162 663 0xe01c
10.3.4.112 10.56.2.4 0x8000b715 1058 0xf4cb
10.3.4.144 10.56.1.4 0x80003162 663 0x8b53
10.3.4.144 10.56.2.4 0x800058dc 1058 0x2e0c
10.3.4.168 10.56.1.4 0x80003162 663 0xae16
10.3.4.168 10.56.2.4 0x800058de 1058 0x25fc
10.3.5.52 10.56.1.4 0x80000f5e 4 0x8ad5
10.3.5.52 10.56.2.4 0x80000f60 1659 0x93c7
10.3.5.80 10.56.1.4 0x80000f60 364 0x81be
10.3.5.80 10.56.2.4 0x80000f65 220 0x5cdf
10.3.5.108 10.56.1.4 0x80000f61 4 0x66bc
10.3.5.108 10.56.2.4 0x80000f61 1659 0x5fc2
10.3.5.136 10.56.1.4 0x8000262a 664 0x62c6
10.3.5.136 10.56.2.4 0x80002632 1059 0x5fbe
10.3.5.164 10.56.1.4 0x80003162 664 0xcbfb
10.3.5.164 10.56.2.4 0x80008351 1059 0xdbab
10.3.5.192 10.56.1.4 0x8000262c 664 0x40ac
10.3.5.192 10.56.2.4 0x80002633 1059 0x2bb9
10.3.5.220 10.56.1.4 0x8000267b 664 0x740f
10.3.5.220 10.56.2.4 0x80002685 1059 0x6d09
10.3.5.248 10.56.1.4 0x8000267c 664 0x6df6
10.3.5.248 10.56.2.4 0x80002686 1059 0x3e1d
10.3.6.20 10.56.1.4 0x8000267f 664 0x4df7
10.3.6.20 10.56.2.4 0x80002686 1059 0x3805
10.3.6.48 10.56.1.4 0x8000011d 1535 0x545e
10.3.6.48 10.56.2.4 0x80000f0d 1149 0x575a
10.3.6.76 10.56.1.4 0x800001be 965 0x ce6
10.3.6.76 10.56.2.4 0x800001be 1749 0xf003
10.3.6.116 10.56.1.4 0x80003162 664 0x8e6a
10.3.6.116 10.56.2.4 0x8000771f 1059 0x4fa3
10.3.6.204 10.56.1.4 0x80003155 664 0x7136
10.3.6.204 10.56.2.4 0x80003162 1059 0x3c5f
10.3.6.208 10.56.1.4 0x80000f54 364 0xc5fe
10.3.6.208 10.56.2.4 0x80000f58 190 0xa21f
10.3.6.244 10.56.1.4 0x80003163 664 0x9bd9
10.3.6.244 10.56.2.4 0x800078d0 1059 0xbb08
10.3.6.248 10.56.1.4 0x80003163 664 0x73fd
10.3.6.248 10.56.2.4 0x800078d9 1059 0x6d4b
10.3.7.68 10.56.1.4 0x80000604 94 0xa30e
10.3.7.68 10.56.2.4 0x80000605 1059 0xaefe
10.3.7.96 10.56.1.4 0x80000604 244 0x9ef4
10.3.7.96 10.56.2.4 0x80000605 1209 0x8112
10.3.7.124 10.56.1.4 0x8000060b 94 0x77f8
10.3.7.124 10.56.2.4 0x8000060d 1179 0x6c01
10.3.8.0 10.56.1.4 0x80003173 1535 0xf661
10.3.8.0 10.56.2.4 0x80005b5c 1749 0x9fa4
10.3.8.40 10.56.1.4 0x80003162 664 0x73cf
10.3.8.40 10.56.2.4 0x80006f3a 1059 0x1614
10.3.8.68 10.56.1.4 0x80003162 664 0x6eb6
10.3.8.68 10.56.2.4 0x80006f65 1059 0x9252
10.3.8.96 10.56.1.4 0x80003162 664 0x55b3
10.3.8.96 10.56.2.4 0x80006f3b 1059 0xe10f
10.3.8.200 10.56.1.4 0x80003162 664 0x415f
10.3.8.200 10.56.2.4 0x80004b62 1059 0xd7af
10.3.9.56 10.56.1.4 0x80000903 1115 0x3b78
10.3.9.56 10.56.2.4 0x80000905 1659 0x1c96
10.3.9.104 10.56.1.4 0x800023e8 664 0x 386
10.3.9.104 10.56.2.4 0x800023f1 1059 0xfd7f
10.3.9.108 10.56.1.4 0x80003162 664 0xd12a
10.3.9.108 10.56.2.4 0x80005a3e 1059 0x8374
10.3.9.124 10.56.1.4 0x8000040c 334 0x5120
10.3.9.124 10.56.2.4 0x8000040b 400 0x600f
10.3.9.152 10.56.1.4 0x8000040b 334 0x4e06
10.3.9.152 10.56.2.4 0x8000040c 400 0x3123
10.3.9.180 10.56.1.4 0x8000040c 334 0x3304
10.3.9.180 10.56.2.4 0x8000040c 400 0x2c0a
10.3.10.44 10.56.1.4 0x80003162 664 0x49f1
10.3.10.44 10.56.2.4 0x80004a1e 1059 0x6bfb
10.3.10.244 10.56.1.4 0x8000040a 394 0x9564
10.3.10.244 10.56.2.4 0x8000040b 430 0xa055
10.3.11.16 10.56.1.4 0x8000040b 394 0x8d4d
10.3.11.16 10.56.2.4 0x8000040c 430 0x706a
10.3.11.44 10.56.1.4 0x8000040a 364 0x7649
10.3.11.44 10.56.2.4 0x8000040c 430 0x6b51
10.3.11.72 10.56.1.4 0x80001f72 514 0x27fa
10.3.11.72 10.56.2.4 0x80001f7a 549 0x24f2
10.3.11.100 10.56.1.4 0x800022a4 785 0xb41a
10.3.11.100 10.56.2.4 0x800022ac 1750 0x893e
10.3.11.128 10.56.1.4 0x80001f73 515 0x 7df
10.3.11.128 10.56.2.4 0x80001f7c 1750 0xedee
10.3.16.0 10.56.1.4 0x80003173 1536 0x86cd
10.3.16.0 10.56.2.4 0x80005b5c 1750 0x2f11
10.3.16.96 10.56.1.4 0x80003162 665 0xbc4c
10.3.16.96 10.56.2.4 0x80004fbb 1060 0xa8e7
10.3.16.160 10.56.1.4 0x80003166 725 0x823a
10.3.16.160 10.56.2.4 0x80003175 790 0x4965
10.6.0.8 10.56.1.4 0x8000040a 425 0x5d8a
10.6.0.8 10.56.2.4 0x8000040b 461 0x40a7
10.6.1.