[j-nsp] self-pointing route resolution: static vs. bgp ?
Alexandre Snarskii
snar at snar.spb.ru
Thu Oct 22 13:30:00 EDT 2015
Hi!
Imagine there is a directly connected network:
A.B.C.40/29 *[Direct/0] 41w1d 00:10:40
> via xe-0/0/2.232
There is a good old trick: you can configure 'self-pointing'
host route with next-hop within this network:
snar at router> show configuration routing-options static route A.B.C.43/32
next-hop A.B.C.43;
it will be accepted, resolved and installed into routing table:
snar at router> show route A.B.C.43/32 detail
A.B.C.43/32 (1 entry, 1 announced)
State: <FlashAll>
*Static Preference: 5
Next hop type: Router, Next hop index: 1256
Address: 0x21a45c90
Next-hop reference count: 5
Next hop: A.B.C.43 via xe-0/0/2.232, selected
(this trick was used before introduction vrf-table-label to install
host routes in vrf's for customers who did not wanted to install CPE).
However, when such self-pointing route is received over iBGP
snar at router> show route A.B.C.42/32 receive-protocol bgp ...
A.B.C.42/32 (1 entry, 0 announced)
Accepted
Nexthop: A.B.C.42
MED: 100
Localpref: 20
AS path: I
it becomes hidden with Unusable next-hop
snar at router> show route A.B.C.42/32 hidden detail
A.B.C.42/32 (1 entry, 0 announced)
BGP Preference: 170/-21
Next hop type: Unusable
Address: 0x24e59bc
Next-hop reference count: 3
State: <Hidden Int Ext>
Accepted
Localpref: 15
Indirect next hops: 1
Protocol next hop: A.B.C.42
Indirect next hop: 0 - INH Session ID: 0x0
and not installed into forwarding table. Well, Juniper documentation
clearly says[1] that it will not accept route pointing to device itself,
but it is not the case, Local address is .41:
A.B.C.41/32 *[Local/0] 44w0d 23:41:25
Local via xe-0/0/2.232
Question: are there any way to convince JunOS to resolve and install
such self-pointing route when received over iBGP ?
12.3R5.7, MX80 if that matters.
[1]:
http://www.juniper.net/techpubs/en_US/junos13.3/topics/concept/hidden-routes-understanding.html
Routes can be hidden for the following reasons:
[...]
The next hop address is the address of the local routing device.
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