OSPF-ISIS Redistribution

JoseBejarano

Hi,

Topology

|----R1

---

R3

---

R5

---

|
| | | | |
10.200.1.0/24 | ospf/isis | 20.20.0.0/21
| | | | |
|

---

R2

---

R4----​

---

R6

---

|

R1,R2,R3+R4 OSPF
R3,R4,R5+R6 ISIS Level 2
R3 and R4 are redistributing ISIS/OSPF
OSPF has external 10.200.1.0/24
ISIS has external 20.20.0.0/21

How would be best to redsitribute ospf/isis on R3 and R4 ? is this topology just creating loops or just suboptimal routing ?
1) using external preference 166 onR3/R4 is not working due same issue on external ospf prefix
2) using tags should work but how to configure them properly ? examples are wellcome

How about loopbacks R3+R4 and directly connected interfaces ?
should be on ISIS AND OSPF protocol stanza ?

Thanks for any feedback and/or hints ?
Jose

JoseBejarano

Forgot to say, i already tried to tag external ISIS 165 when redistributing from isis to ospf and filter when importing to OSPF on R3 and R4 under OSPF protocol but still external OSPF 150 didnt work, any ideas ?

EXPORT
policy-statement isis2ospf {
term 1 {
from {
protocol isis;
route-filter 20.20.0.0/21 orlonger;
}
then {
tag 123;
accept;
}
}
term 2 {
from protocol isis;
then accept;
}
}

IMPORT
policy-statement import-ospf {
term 1 {
from {
protocol ospf;
tag 123;
}
then reject;
}
term 2 {
then accept;
}
}

hoogen82

How about isis wide metrics...

JoseBejarano

Hoogen,

am i understanding this right ?

Configuring wide-metrics-only on R5 + R6 ( RIP injecting externals ) will considered external ISIS prefixes as internals on R3 + R4. L2 internals are Default Preference 18 and better than OSPF External 150.

Is there any other tip/hint about ISIS/OSPF 2xredistribution points ? Everything seems to be working as expected but not sure if any other issue related to routing loops and/or suboptimal path. Any problem i could find was just the one for the L2 external prefixes....

Thanks again for the very helpful advice ,
Jose

hoogen82

That would definitely help... Have you lab'ed this up... That would really help solve your problems...

Sorry for the delayed response...

JoseBejarano

Hi Hoogen,

Thanks, sure, it works as you said after configuring wide-metrics-only. I am still working out how to approach redistribution on ISIS/OSPF.
1) wide-metrics-only on ISIS routers + redistribute specific prefixes using route-filters from ISIS into OSPF and viceversa including directly connected ifs.
2) wide-metrics-only on ISIS routers + redistribute ALL ( from protocol ) from ISIS into OSPF and viceversa including directly connected ifs.
3) same as 2) but tagging everything on 1x protocol and rejecting everything coming back with same tag.

Any recommendation ?

Cheers,
Jose