One would hope that the developers of a network operating system wouldn’t feel the irresistible urge to reinvent what should have been a common configuration feature for every routing protocol. Alas, the IOS/XR developers failed to get that memo.

I decided to implement route redistribution (known as route import in netlab) for OSPFv2/OSPFv3, IS-IS, and BGP on IOS/XR (Cisco 8000v running IOS/XR release 24.4.1) and found that each routing protocol uses a different syntax for the source routing protocol part of the redistribute command.

Here’s how one can redistribute OSPF routes into BGP:

RP/0/RP0/CPU0:dut(config)#router bgp 123
RP/0/RP0/CPU0:dut(config-bgp)#addr ipv4 unicast
RP/0/RP0/CPU0:dut(config-bgp-af)#redistribute ospf 1 match internal external ?
  1              Redistribute external type 1 routes
  2              Redistribute external type 2 routes
  metric         Metric for redistributed routes
  multipath      Enable installation of multiple paths from RIB
  nssa-external  Redistribute OSPF NSSA external routes
  route-policy   Route policy reference
  <cr>

Having Cisco IOS battle scars, I decided to be on the safe side and use match internal external nssa-external to redistribute every possible route type from OSPF into BGP¹.

The same command syntax does not work when redistributing OSPF into IS-IS:

RP/0/RP0/CPU0:dut(config)#router isis Gandalf
RP/0/RP0/CPU0:dut(config-isis)#address-family ipv4 unicast
RP/0/RP0/CPU0:dut(config-isis-af)#redistribute ospf 1 match ?
  external       Redistribute OSPF external routes
  internal       Redistribute OSPF internal routes
  nssa-external  Redistribute OSPF NSSA external routes
RP/0/RP0/CPU0:dut(config-isis-af)#redistribute ospf 1 match internal ?
  level-1       Redistribute routes into level 1 only
  level-1-2     Redistribute routes into both levels
  level-2       Redistribute routes into level 2 only (the default)
  metric        Metric for redistributed routes
  metric-type   IS-IS metric type for redistributed routes
  route-policy  Route policy reference
  <cr>

You cannot specify more than one OSPF route type in the redistribute command, and if you try to enter two redistribute ospf commands, the second one overwrites the first one, even though they have different match requirements. Lovely. In the end, I gave up and used the simple redistribute ospf pid command. Some routes are bound to get from OSPF to IS-IS².

Redistributing IS-IS into OSPF or BGP is no better. Here’s the IS-IS-to-BGP syntax:

RP/0/RP0/CPU0:dut(config)#router bgp 123
RP/0/RP0/CPU0:dut(config-bgp)#address-family ipv4 unicast
RP/0/RP0/CPU0:dut(config-bgp-af)#redistribute isis Gandalf level ?
  1             Redistribute ISIS level 1 routes
  1-inter-area  Redistribute ISIS level 1 inter-area routes
  2             Redistribute ISIS level 2 ISIS routes
RP/0/RP0/CPU0:dut(config-bgp-af)#redistribute isis Gandalf level 1 ?
  level         Redistribute routes from the specified ISIS levels
  metric        Metric for redistributed routes
  multipath     Enable installation of multiple paths from RIB
  route-policy  Route policy reference
  <cr>

You have to use redistribute isis instance level 1 level 2 to redistribute all IS-IS routes into BGP.
And here’s how you redistribute IS-IS into OSPF:

RP/0/RP0/CPU0:dut(config)#router ospf 1
RP/0/RP0/CPU0:dut(config-ospf)#redistribute isis level ?
  level-1       IS-IS level-1 routes only
  level-1-2     IS-IS level-1 and level-2 routes
  level-2       IS-IS level-2 routes only
  lsa-type      LSA type for redistributed routes
  metric        Metric for redistributed routes
  metric-type   OSPF exterior metric type for redistributed routes
  nssa-only     Redistribute to NSSA areas only
  route-policy  Apply route-policy to redistribution
  tag           Set tag for routes redistributed into OSPF
  <cr>

The command to use to redistribute all IS-IS routes into OSPF is now redistribute isis instance level-1-2.

One might not care about such minor inconsistencies (apart from yelling at the box when the fingers are faster than the conscious brain) when doing manual configuration, but they’re soul-drainingly irritating³ (as is the IOS/XR boot time) when you try to create reusable configuration templates. However, I don’t expect anything to change until we start voting with our wallets.