RE: OSPF LSAs [7:54293]
I do not have the book with me right now, but I do know that regarding E2, the internal cost is not condidered!! I will check the book later and see! Trying to remember for tomorrow!! Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54295&t=54293 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF LSAs [7:54293]
The second is definitely correct. The first is also correct if you consider the "cost of the path to the ASBR" as the cost of the path from the destination network to the ASBR, but not if you consider it as the cost to get to the ASBR across the OSPF network. E1 cost = external metric + OSPF path cost E2 cost = external metric E1 is always preferred to E2 if both exist, regardless of the individual metrics. Hope this helps... -- Russell Heilling http://www.ccie.org.uk/ ""Matthew Webster"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I studying the CiscoPress CCNP Routing Book at the moment. There appears to > be a contradiction on page 294 and 295. on page 294: the path to another AS > can be calculated in one of two ways. The second way (E2) states that the > cost of the path to the ASBR is all that is considered in the equation. > However in table 6-2 on p.295 it states that LSA type 5, in relatino to E2 > "dopes not compute the internal cost - it just reports the external cost to > eh remote destination". This seems to be the opposite of the previosu > statement. > > Can any advise which way round it is (although I think it is the cost to the > ASBR, and not the cost from the ASBR to the remote destination). > > Cheers, > Matthew. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54305&t=54293 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF LSAs [7:54293]
Mathew An easy way to remember is that E1 metrics are comparable with the intra-AS costs and thus adding intra-AS costs makes a significant change to total costs. E2 metrics on the other hand are magnitudes greater than intra-AS costs so adding intra-AS costs will be an insignificant change. This is why E1=external metric + Intra-AS cost and E2=external metric Hope this helps Regards, Michael -Original Message- From: Matthew Webster [mailto:[EMAIL PROTECTED]] Sent: 27 September 2002 02:23 AM To: [EMAIL PROTECTED] Subject: OSPF LSAs [7:54293] I studying the CiscoPress CCNP Routing Book at the moment. There appears to be a contradiction on page 294 and 295. on page 294: the path to another AS can be calculated in one of two ways. The second way (E2) states that the cost of the path to the ASBR is all that is considered in the equation. However in table 6-2 on p.295 it states that LSA type 5, in relatino to E2 "dopes not compute the internal cost - it just reports the external cost to eh remote destination". This seems to be the opposite of the previosu statement. Can any advise which way round it is (although I think it is the cost to the ASBR, and not the cost from the ASBR to the remote destination). Cheers, Matthew. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54307&t=54293 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF LSAs [7:54293]
At 12:23 AM + 9/27/02, Matthew Webster wrote: >I studying the CiscoPress CCNP Routing Book at the moment. As I've always understood from the IETF: E1 metric = sum of internal costs of reaching ASBR + external cost of ASBR E2 metric = external cost of ASBR. > There appears to >be a contradiction on page 294 and 295. on page 294: the path to another AS >can be calculated in one of two ways. The second way (E2) states that the >cost of the path to the ASBR is all that is considered in the equation. If the cost of the ASBRs is equal, you get the effect of this as the E1 metric, but this is not implicit in the protocol. >However in table 6-2 on p.295 it states that LSA type 5, in relatino to E2 >"dopes not compute the internal cost - it just reports the external cost to >eh remote destination". This seems to be the opposite of the previosu >statement. This is the E2 metric. > >Can any advise which way round it is (although I think it is the cost to the >ASBR, and not the cost from the ASBR to the remote destination). > >Cheers, >Matthew. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54312&t=54293 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF LSAs [7:54293]
At 12:23 AM + 9/27/02, Matthew Webster wrote: >I studying the CiscoPress CCNP Routing Book at the moment. As I've always understood from the IETF: E1 metric = sum of internal costs of reaching ASBR + external cost of ASBR E2 metric = external cost of ASBR. > There appears to >be a contradiction on page 294 and 295. on page 294: the path to another AS >can be calculated in one of two ways. The second way (E2) states that the >cost of the path to the ASBR is all that is considered in the equation. If the cost of the ASBRs is equal, you get the effect of this as the E1 metric, but this is not implicit in the protocol. >However in table 6-2 on p.295 it states that LSA type 5, in relatino to E2 >"dopes not compute the internal cost - it just reports the external cost to >eh remote destination". This seems to be the opposite of the previosu >statement. This is the E2 metric. > >Can any advise which way round it is (although I think it is the cost to the >ASBR, and not the cost from the ASBR to the remote destination). > >Cheers, >Matthew. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54320&t=54293 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF LSAs [7:54293]
The entire chapter on OSPF in that book is dangerous. I would recommend that you find another source to study OSPF or you may walk away with a very unfortunate understanding of that particular routing protocol. Beware especially of any discussion involving an ASBR. Matthew Webster wrote: > > I studying the CiscoPress CCNP Routing Book at the moment. > There appears to be a contradiction on page 294 and 295. on > page 294: the path to another AS can be calculated in one of > two ways. The second way (E2) states that the cost of the path > to the ASBR is all that is considered in the equation. However > in table 6-2 on p.295 it states that LSA type 5, in relatino to > E2 "dopes not compute the internal cost - it just reports the > external cost to eh remote destination". This seems to be the > opposite of the previosu statement. > > Can any advise which way round it is (although I think it is > the cost to the ASBR, and not the cost from the ASBR to the > remote destination). > > Cheers, > Matthew. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54322&t=54293 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF LSAs [7:54293]
Hi all, thanks all for your comments. It certainly is clearer in my mind that E2 is the external metric cost...i.e. from the ASBR to the destination host, and is not the intra-area cost from the originating host to the ASBR. Also appreciated the last comment about the chapter overall and will keep an eye out for other chapters. cheers, Matthew. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54505&t=54293 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
