From: Alexander Arsenyev (GU/ETL) (alexander.arsenyev@ericsson.com)
Date: Sun Nov 21 2004 - 23:35:10 GMT-3
Hello,
The virtual link has to be associated with virtual interfaces on both ends.
Virtual interfaces' IP addresses are used to send OSPF packets over VL.
Thats' what the quote below says.
There is another quote in RFC2328 which explains how virtual interface' IP
addresses are selected (section 16(4)):
<quote>
If Router X is the endpoint of one of the
calculating router's virtual links, and the virtual link
uses Area A as Transit area: the virtual link is declared
up, the IP address of the virtual interface is set to the IP
address of the outgoing interface calculated above for
Router X, and the virtual neighbor's IP address is set to
Router X's interface address (contained in Router X's
router-LSA) that points back to the root of the shortest-
path tree..
</quote>
What it says is:
1) to assign IP address of own virtual interface use IP address of outgoing
interface which is used to reach virtual neighbor Router ID
2) for virtual neighbor's IP address (it is used as destination IP in OSPF VL packet)
examine router LSA from virtual neighbor and use one of IP addresses found there.
3) now let's see how router LSAs for unnumbered p-t-p links are built:
<quote from RFC2328 section 12.4.1>
The router-LSA then describes the router's working
connections (i.e., interfaces or links) to the area. Each
link is typed according to the kind of attached network.
Each link is also labelled with its Link ID....
....In addition, the Link Data field is specified for each link.
This field gives 32 bits of extra information for the link.
For links to transit networks, numbered point-to-point links
and virtual links, this field specifies the IP interface
address of the associated router interface (this is needed
by the routing table calculation, see Section 16.1.1). For
links to stub networks, this field specifies the stub
network's IP address mask. For unnumbered point-to-point
links, the Link Data field should be set to the unnumbered
interface's MIB-II [Ref8] ifIndex value.
</quote>
In other words, if the only connection to transit area is via unnumbered p-t-p link
the router LSA sent into this transit area will have MIB-II ifIndex value as Link Data.
Of course, it is umpossible to use ifIndex as destination IP.
Makes sense?
HTH,
Cheers
Alex
P.S. I would suggest to build a parallel path between these 2 routers using normal numbered
links and see if VL comes up.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Vytautas Valancius
Sent: 21 November 2004 22:43
To: ccielab@groupstudy.com
Subject: Re: virtual links over ip unnumbered
Hi Group,
I found a hint on virtual-link problem i have. My guess is that it is
impossible to build up virtual link if at least one of the routers is
connected to transit area only with ip unnumbered link. Here is an excerpt
from RFC2328:
--- Just as the virtual link's cost and viability are determined by the routing table build process (through construction of the routing table entry for the other endpoint), so are the IP interface address for the virtual interface and the virtual neighbor's IP address. These are used when sending OSPF protocol packets over the virtual link. Note that when one (or both) of the virtual link endpoints connect to the Transit area via an unnumbered point-to-point link, it may be impossible to calculate either the virtual interface's IP address and/or the virtual neighbor's IP address, thereby causing the virtual link to fail. ---As you see it is not clearly stated that link will definately fail. It is writen 'may'. Any ideas on what topology virtual-link with ip unnumbered would work?
Cheers, Vytautas Valancius
----- Original Message ----- From: "Vytautas Valancius" <valas@mail.lt> To: <ccielab@groupstudy.com> Sent: Sunday, November 21, 2004 4:50 PM Subject: Re: virtual links over ip unnumbered
> Hi Group, > > Can anybody confirm that they succeed in running direct OSPF virtual-link > over ip > unnumebered? Maybe it is not possible to do and I'm sticking to this problem > too much. > > Cheers, > Vytautas Valancius > > ----- Original Message ----- > From: "Vytautas Valancius" <valas@mail.lt> > To: <ccielab@groupstudy.com> > Sent: Sunday, November 21, 2004 12:51 AM > Subject: Re: virtual links over ip unnumbered > > > > Hi, > > > > Below are super simple configurations for two routers connected with > serial > > line. > > > > Virtual links are down even in this simple config. Network 172.16.100.0/24 > > is not in R1 because of that. As I said more interesting things happen > when > > we have complex ISDN setup, but I guess before debuging that one should > > understand why this simple configuration is not working... > > > > There are no error messages. 'debug ip ospf adj' does not show any output. > > 'debug ip ospf packet' behaves as there is no virtual link configured - no > > packets are sent ir received to establish it. > > > > R1: > > ! > > interface Loopback1 > > description area 0 > > ip address 172.16.1.1 255.255.255.0 > > ip ospf network point-to-point > > ! > > interface Loopback101 > > ip address 172.16.101.1 255.255.255.0 > > ip ospf network point-to-point > > ! > > interface Serial4/6 > > ip unnumbered Loopback101 > > ! > > router ospf 1 > > router-id 172.16.101.1 > > log-adjacency-changes > > area 16 virtual-link 172.16.106.1 > > passive-interface Loopback1 > > network 172.16.1.1 0.0.0.0 area 0 > > network 172.16.101.1 0.0.0.0 area 16 > > ! > > > > R1#sh ip ospf nei > > > > Neighbor ID Pri State Dead Time Address > Interface > > 172.16.106.1 1 FULL/ - 00:00:39 172.16.106.1 > Serial4/6 > > > > R1#sh ip ospf virtual-links > > Virtual Link OSPF_VL0 to router 172.16.106.1 is down > > Run as demand circuit > > DoNotAge LSA allowed. > > Transit area 16, Cost of using 65535 > > Transmit Delay is 1 sec, State DOWN, > > Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 > > > > R1#ping 172.16.106.1 > > > > Type escape sequence to abort. > > Sending 5, 100-byte ICMP Echos to 172.16.106.1, timeout is 2 seconds: > > !!!!! > > Success rate is 100 percent (5/5), round-trip min/avg/max = 16/16/20 ms > > R1#sh ip ro > > Gateway of last resort is not set > > > > 172.16.0.0/24 is subnetted, 3 subnets > > C 172.16.1.0 is directly connected, Loopback1 > > O 172.16.106.0 [110/782] via 172.16.106.1, 00:04:47, Serial4/6 > > C 172.16.101.0 is directly connected, Loopback101 > > > > > > R6 output: > > ! > > interface Loopback100 > > description area 100 > > ip address 172.16.100.1 255.255.255.0 > > ip ospf network point-to-point > > ! > > interface Loopback106 > > ip address 172.16.106.1 255.255.255.0 > > ip ospf network point-to-point > > ! > > interface Serial0 > > ip unnumbered Loopback106 > > no fair-queue > > clockrate 125000 > > ! > > interface Serial1 > > no ip address > > shutdown > > ! > > router ospf 1 > > router-id 172.16.106.1 > > log-adjacency-changes > > area 16 virtual-link 172.16.101.1 > > network 172.16.100.1 0.0.0.0 area 100 > > network 172.16.106.1 0.0.0.0 area 16 > > ! > > R6#sh ip ospf nei > > > > Neighbor ID Pri State Dead Time Address > Interface > > 172.16.101.1 1 FULL/ - 00:00:33 172.16.101.1 Serial0 > > R6# > > R6#sh ip os > > R6#sh ip ospf vir > > Virtual Link OSPF_VL0 to router 172.16.101.1 is down > > Run as demand circuit > > DoNotAge LSA allowed. > > Transit area 16, Cost of using 65535 > > Transmit Delay is 1 sec, State DOWN, > > Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 > > > > R6#ping 172.16.101.1 > > > > Type escape sequence to abort. > > Sending 5, 100-byte ICMP Echos to 172.16.101.1, timeout is 2 seconds: > > !!!!! > > Success rate is 100 percent (5/5), round-trip min/avg/max = 16/16/20 ms > > R6# > > R6#sh ip ro > > > > Gateway of last resort is not set > > > > 172.16.0.0/24 is subnetted, 4 subnets > > O IA 172.16.1.0 [110/65] via 172.16.101.1, 00:04:34, Serial0 > > C 172.16.106.0 is directly connected, Loopback106 > > C 172.16.100.0 is directly connected, Loopback100 > > O 172.16.101.0 [110/65] via 172.16.101.1, 00:04:44, Serial0 > > > > > > ----- Original Message ----- > > From: "ccie2be" <ccie2be@nyc.rr.com> > > To: "Vytautas Valancius" <valas@mail.lt>; <ccielab@groupstudy.com> > > Sent: Sunday, November 21, 2004 12:59 AM > > Subject: Re: virtual links over ip unnumbered > > > > > > > Could you post your configuration? Including show command output? And, > > > error messages? > > > ----- Original Message ----- > > > From: "Vytautas Valancius" <valas@mail.lt> > > > To: <ccielab@groupstudy.com> > > > Sent: Saturday, November 20, 2004 2:37 PM > > > Subject: virtual links over ip unnumbered > > > > > > > > > > Hi Group, > > > > > > > > Does OSPF virtual-link work over link with ip unnumbered on both > sides? > > > > > > > > I did not succed to run it in pretty basic setups. Moreover, if I run > it > > > > over unnumbered ISDN, demand-circuit feature is not working. Virtual > > link > > > is > > > > UP only on one side and it keeps sending OSPF messages that brings > ISDN > > up > > > > imediatelly after it goes down. > > > > > > > > Any comments are welcomed! > > > > > > > > valas > > > > > > > > > _______________________________________________________________________ > > > > Subscription information may be found at: > > > > http://www.groupstudy.com/list/CCIELab.html > > > > _______________________________________________________________________ > > Subscription information may be found at: > > http://www.groupstudy.com/list/CCIELab.html > > _______________________________________________________________________ > Subscription information may be found at: > http://www.groupstudy.com/list/CCIELab.html
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