From: Brian McGahan (brian@cyscoexpert.com)
Date: Thu Dec 26 2002 - 20:06:24 GMT-3
Jerry,
There are two types of authentication in OSPF, area and
interface. If area authentication is enabled, all interfaces which have
adjacencies on them must authenticate. A virtual-link *is* an area 0
interface, therefore if you have a virtual-link, and are authenticating
area 0, you must authenticate the virtual-link.
Interface authentication is independent of area authentication,
and interface authentication overrides area authentication. This means
that you could be using clear-text authentication throughout and area,
and implement md5 authentication on a particular link within that area.
In the case that you have presented, interface authentication is enabled
on the virtual-link. This is a perfectly valid configuration.
If in your example you had said 'area 0 authentication', the
remote router where the virtual-link terminates would also have to say
'area 0 authentication'. It is not completely necessary that you
configure a key on the interface (or virtual-link in this case). OSPF
authentication uses a "null" key by default. Practically, security
through obscurity is not a very safe practice, therefore you should
configure a key on each interface which is authenticating.
HTH
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
Voice: 847.674.3392
Fax: 847.674.2625
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Jerry Haverkos
> Sent: Thursday, December 26, 2002 2:42 PM
> To: 'Lysyuk Andrew'
> Cc: ccielab@groupstudy.com
> Subject: RE: Help me pls with OSPF authentication.
>
> Lysuk
>
> I am on IOS 12.1.13 and my configs show no correlation between
> authentication of area 0 and authentication on the virtual link. The
> following are excerpts from my configs on the router that houses area
0
> and
> participates as part of the virtual link in my network. They show that
> there
> is no correlation in my network.
>
> 3640-1_R1#sho ip ospf virtual-links
> Virtual Link OSPF_VL0 to router 0.0.0.4 is up
> Run as demand circuit
> DoNotAge LSA allowed.
> Transit area 4, via interface Serial1/0.4, Cost of using 781
> Transmit Delay is 1 sec, State POINT_TO_POINT,
> Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
> Hello due in 00:00:05
> Adjacency State FULL (Hello suppressed)
> Index 1/4, retransmission queue length 0, number of retransmission
1
> First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
> Last retransmission scan length is 1, maximum is 1
> Last retransmission scan time is 0 msec, maximum is 0 msec
> Message digest authentication enabled
> Youngest key id is 1
>
>
> Note -- on the router there is only one interface in area 0 and it
does
> not
> specify authentication
>
> 3640-1_R1#
> router ospf 100
> router-id 0.0.0.1
> log-adjacency-changes
> no discard-route internal
> area 0 range 149.1.254.0 255.255.255.0
> area 0 range 149.1.0.0 255.255.0.0
> area 1 range 149.1.1.0 255.255.255.0
> area 2 authentication message-digest
> area 2 stub no-summary
> area 2 range 149.1.2.0 255.255.255.0
> area 4 range 149.1.4.0 255.255.255.0
> area 4 virtual-link 0.0.0.4 authentication message-digest
> area 4 virtual-link 0.0.0.4 message-digest-key 1 md5 cubbies
> area 5 authentication message-digest
> area 5 nssa no-summary
> area 5 range 149.1.5.0 255.255.255.0
> summary-address 17.0.0.0 255.0.0.0 not-advertise
> network 149.1.1.0 0.0.0.255 area 1
> network 149.1.2.0 0.0.0.255 area 2
> network 149.1.4.0 0.0.0.255 area 4
> network 149.1.5.0 0.0.0.255 area 5
> network 149.1.254.254 0.0.0.0 area 0
> neighbor 149.1.2.254
> neighbor 149.1.4.254
> neighbor 149.1.5.254
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Justin Menga
> Sent: Thursday, December 26, 2002 1:11 AM
> To: Jude Servi; 'Robert Slaski'; 'Manish Gupta'
> Cc: 'Lysyuk Andrew'; ccielab@groupstudy.com
> Subject: RE: Help me pls with OSPF authentication.
>
>
> Also, if you enable authentication for a virtual link, you must also
> ensure
> area 0 has authentication enabled:
>
> router ospf 1
> area 0 authentication
> area 1 virtual-link .....
>
> Regards,
> Justin
>
> -----Original Message-----
> From: Jude Servi [mailto:jservi@cisco.com]
> Sent: Wednesday, December 25, 2002 12:36 PM
> To: 'Robert Slaski'; 'Manish Gupta'
> Cc: 'Lysyuk Andrew'; ccielab@groupstudy.com
> Subject: RE: Help me pls with OSPF authentication.
>
>
> Don't forget to add authentication to a virtual link if needed.
Example
> for
> md5 auth:
>
> router ospf 1
> area # virtual-link <neighbor ip addr> authentication message-digest
> message-digest-key # <key>
>
> Jude
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Robert Slaski
> Sent: Saturday, December 21, 2002 11:16 AM
> To: Manish Gupta
> Cc: Lysyuk Andrew; ccielab@groupstudy.com
> Subject: Re: Help me pls with OSPF authentication.
>
>
> Manish Gupta wrote:
> > I always prefer
> >
> > Under router ospf x
> > area x authentication (plain or MD5)
> >
> > Under interface:
> > ip opsf authetication <password> if plain
>
> You meant 'ip ospf authentication-key' I think, but this does not
answer
>
> the Andrew's question.
>
> There are two authentication types available in OSPF: per area and per
> interface, if both are configured then per interface authentication
> takes precedence. Both have plain-text and MD5 checksum variants.
>
> Per area:
> 1. enable area authentication
> (config-router)# area <area> authentication [message-digest]
> 2. setup keys (this should be done on each area interface)
> (config-if)# ip ospf authentication-key <text> # for plain text
> or
> (config-if)# ip ospf message-digest-key <key_id> md5 0 <text> # for
MD5
>
> Per interface:
> 1. enable interface authentication
> (config-if)# ip ospf authentication [message-digest | null]
> 2. setup keys (same as above)
>
> mikrobi,
> --
> .
> .
.
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