Hi Joakim,
While it certainly isn't described very well, the intent is that the
second router link is omitted for unnumbered links. If you look at
the example for RT3's backbone area router LSA on page 134, you'll
note the omission.
; RT3's router-LSA for the backbone
LS age = 0 ;always true on origination
Options = (E-bit) ;
LS type = 1 ;indicates router-LSA
Link State ID = 192.1.1.3 ;RT3's router ID
Advertising Router = 192.1.1.3 ;RT3's router ID
bit E = 0 ;not an AS boundary router
bit B = 1 ;area border router
#links = 1
Link ID = 18.10.0.6 ;Neighbor's Router ID
Link Data = 0.0.0.3 ;MIB-II ifIndex of P-P link
Type = 1 ;connects to router
# TOS metrics = 0
metric = 8
I'll keep this in my list of RFC 2328 inaccuracies.
Thanks,
Acee
On Jan 6, 2009, at 11:18 AM, Joakim Tjernlund wrote:
In RFC 2328, Chap 12.4.1.1, reads:
12.4.1.1. Describing point-to-point interfaces
For point-to-point interfaces, one or more link
descriptions are added to the router-LSA as follows:
o If the neighboring router is fully adjacent, add a
Type 1 link (point-to-point). The Link ID
should be
set to the Router ID of the neighboring router.
For
numbered point-to-point networks, the Link Data
should specify the IP interface address. For
unnumbered point-to-point networks, the Link Data
field should specify the interface's MIB-II [Ref8]
ifIndex value. The cost should be set to the
output
cost of the point-to-point interface.
o In addition, as long as the state of the interface
is "Point-to-Point" (and regardless of the
neighboring router state), a Type 3 link (stub
network) should be added. There are two forms that
this stub link can take:
Option 1
Assuming that the neighboring router's IP
address is known, set the Link ID of the
Type 3
link to the neighbor's IP address, the Link
Data
to the mask 0xffffffff (indicating a host
route), and the cost to the interface's
configured output cost.[15]
Option 2
If a subnet has been assigned to the point-to-
point link, set the Link ID of the Type 3 link
to the subnet's IP address, the Link Data
to the
subnet's mask, and the cost to the interface's
configured output cost.[16]
I have a hard time figuring out what to do with Option 1 and Option
2 for unnumbered
PtoP interfaces. I don't think either of them applies to an
unnumbered link so
I wonder if one should omit both Options?
However 12.4.1.1 starts with:
For point-to-point interfaces, one or more link
descriptions are added to the router-LSA as follows
which could be read as there must always be one or more items and
as the first
item needs to have a fully adjacent router you could end up with
zero items in the LSA for
a PtoP interface.
So what should one do?
Jocke
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