Hi,
I'm seeing a problem with route redistribution that I hope someone can
help with...
When redistributing a default route from iBGP to OSPF, other OSPF
routers do not seem to respect the value of ospf_metric2 set on
exported routes. If I define the default route in a static protocol
instead of redistributing it, I do not see the problem.
I *think* I see a clue in the output from "show ospf state" below in
the two cases. When using a static protocol, there are different route
distances for each default route- 0 and 10. When doing route
redistribution, both routers show a distance of 65535. That seems odd,
and I'm not sure why it is. Also note that all iBGP peerings are IPv6,
so BGP-MP is in use.
The topology is as follows:
^ ^
| |
eBGP eBGP
| |
+------+ +------+
| gw1 |-----------------------------------------| gw2 |
+--+---+ <-- 0.0.0.0/0 ---+---+--+
| | \ iBGP / | |
| | \ / | |
| | \ / | |
| | \ / | |
| 0.0.0.0/0 \ / 0.0.0.0/0 |
| | iBGP \ \ / / iBGP | |
| v v \ / v v |
| \ / |
| \ / |
| \ / |
| x |
| / \ |
| / \ |
| / \ |
| ^ ^ / \ ^ ^ |
| | iBGP / / \ \ iBGP | |
| A.B.C.D/X / \ A.B.C.D/X |
| | / \ | |
| | / \ | |
| | / \ | |
| | / \ | |
+--+---+ +---+--+
| nat1 |-----------------------------------------| nat2 |
+------+ +------+
| |
OSPF OSPF
E2 metric 10 E2 metric 100
0.0.0.0/0 0.0.0.0/0
| |
v v
* Four routers in an iBGP full mesh
* gw1 and gw2 are the ASBRs, with full BGP tables
* nat1 and nat2 are core routers doing NAT44
* NOTE: all iBGP peerings are IPv6 only, so BGP-MP is in use
* Default route:
* exported by gw1 and gw2 using iBGP
* imported by nat1 and nat2 using iBGP
* redistributed by nat1 and nat2 using OSPF into the LAN
* Different metrics from nat1 and nat2 seem not to be respected
* Problem occurs on both BIRD 2.0.12 and 2.17.1
-----------------------------------------------------------------------
STATIC PROTOCOL (what works)
If I define default routes in a static protocol on nat1 and nat2, and
set ospf_metric2 on an export filter, it works as expected. Routers on
the LAN respect the metric and prefer the route from nat1.
#
# Routing table on another OSPF host running BIRD
#
# Regardless of which order nat1 and nat2 are started in, the
# default route chosen is the one with the lower metric, as expected.
#
bird> show ospf state ospf4
area 0.0.0.0
router <gw1 IPv4 IP>
distance 0
...
external 0.0.0.0/0 metric2 10
router <gw2 IPv4 IP>
distance 10
...
external 0.0.0.0/0 metric2 100
bird> show route for 0.0.0.0/0 all
Table master4:
0.0.0.0/0 unicast [ospf4 09:26:57.341] * E2 (150/65535/10)
[<gw1 IPv4 IP>]
via <gw1 IPv4 IP> on eth0
Type: OSPF-E2 univ
OSPF.metric1: 65535
OSPF.metric2: 10
OSPF.tag: 0x00000000
OSPF.router_id: <gw1 IPv4 IP>
#
# Partial config from gw1/gw2...
#
# NO_KERNEL_EXPORT, if defined, flags a route for NOT exporting to the
# kernel.
attribute int NO_KERNEL_EXPORT;
# IBGP_EXPORT, if defined, flags a route for export to iBGP peers.
attribute int IBGP_EXPORT;
ipv4 table Tibgp4;
# default route injected on gw1/gw2 with static protocol into custom
table
protocol static Sibgp4 {
ipv4 {
table Tibgp4;
import filter {
IBGP_EXPORT = 1;
NO_KERNEL_EXPORT = 1;
accept;
};
};
route 0.0.0.0/0 unreachable;
}
# pipe to master
protocol pipe Pibgp4 {
table master4;
peer table Tibgp4;
import where !defined(NO_KERNEL_EXPORT);
export where defined(IBGP_EXPORT);
}
# sample peering for nat1, with a bunch of things left out
protocol bgp nat1 from IBGP {
ipv4 {
...
table Tibgp4;
export where defined(IBGP_EXPORT);
};
ipv6 {
...
table Tibgp6;
export where defined(IBGP_EXPORT);
};
# anonymized addresses below, but shows that IPv6 LLA is used
interface "bond0.A";
source address fe80::A:1;
neighbor fe80::A:2 internal;
...
}
#
# Partial config for nat1/nat2...
#
# Default route added in a static protocol. This works.
protocol static Sospf4 {
ipv4 {
table Tospf4;
import filter {
OSPF_EXPORT = 1;
accept;
};
};
route 0.0.0.0/0 unreachable;
}
# ospf_metric2 set on an export filter.
protocol ospf v2 ospf4 {
ipv4 {
table Tospf4;
import all;
export filter {
if !defined(OSPF_EXPORT) then reject;
ospf_metric2 = 10; # for nat1, or 100 for nat2
accept;
};
};
...
}
-----------------------------------------------------------------------
ROUTE REDISTRIBUTION (what does not work)
#
# Routing table on another OSPF host running BIRD
#
# !!! Even though nat1 and nat2 are both running, and nat2 has a
# lower value for OSPF.metric2, its default route is not chosen.
# The default route in the OSPF database is from the router that
# started first.
bird> show ospf state ospf4
area 0.0.0.0
...
router <gw1 IPv4 IP>
# !!! distance is 65535- with static protocol it's 0
distance 65535
...
# default route not present when started second
router <gw2 IPv4 IP>
# !!! distance is 65535- with static protocol it's 10
distance 65535
...
# external default route with higher metric 100 is
used
external 0.0.0.0/0 metric2 100
# The default route is gw2, which is unexpected when it has a
# higher metric2.
bird> show route for 0.0.0.0/0 all
Table master4:
0.0.0.0/0 unicast [ospf4 08:37:10.342] * E2 (150/65535/100)
[<gw2
IPv4 IP>]
via <gw2 IPv4 IP> on eth0
Type: OSPF-E2 univ
OSPF.metric1: 65535
OSPF.metric2: 100
OSPF.tag: 0x00000000
OSPF.router_id: <gw2 IPv4 IP>
#
# Config for gw1/gw2 is same as above, when using static protocol...
#
#
# Partial config from nat1/nat2...
#
# OSPF_EXPORT, if defined, flags a route for export via OSPF.
attribute int OSPF_EXPORT;
ipv4 table Tibgp4;
# ibgp_in_primary4 filters primary IPv4 routes imported via iBGP.
filter ibgp_in_primary4 {
if net = 0.0.0.0/0 then {
OSPF_EXPORT = 1;
}
bgp_local_pref = 100;
accept;
}
# pipe to master
protocol pipe Pibgp4 {
table master4;
peer table Tibgp4;
import all;
export where defined(IBGP_EXPORT);
}
protocol bgp gw1 from IBGP {
description "gw1 - VLAN 3313";
ipv4 {
table Tibgp4;
import filter ibgp_in_primary4;
export where defined(IBGP_EXPORT);
...
};
ipv6 {
table Tibgp6;
import filter ibgp_in_primary6;
export where defined(IBGP_EXPORT);
...
};
interface "bond0.A";
source address fe80::A:2;
neighbor fe80::A:1 internal;
...
}
# ospf_metric2 set on an export filter the same as with the static
# protocol case, but the metric seems to not be respected when
# the route is redistributed from iBGP.
protocol ospf v2 ospf4 {
ipv4 {
table Tospf4;
import all;
export filter {
if !defined(OSPF_EXPORT) then reject;
ospf_metric2 = 10; # 10 for nat1, 100 for nat2
accept;
};
};
...
}
Thanks in advance for any help...
Pete
