No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

A Method of Calculating Route Prefixes on the NE40 and the NE80 With the Appendix E Problem

Publication Date:  2012-07-27 Views:  46 Downloads:  0
Issue Description
Fields such as OSPF Old Lsa and OSPF New Lsa that appear in the logs of the NE40/NE80 routers of the V3.10 version indicate problems described in Appendix E of RFC 2328. This case describes how to determine the route prefixes and advertising routers according to the printed log information for the purpose of troubleshooting related problems.  
Alarm Information
%Jan 13 10:53:55 2009 ABC RM/5/RTLOG:
[OSPF LOG] 2009/01/13 10:53:55 - 246490
[OSPF] OSPF Old Lsa:
0e 10 20 02 85 69 a2 03 85 68 ff e5 80 00 09 14
4e 1f 00 20 ff ff ff 80 85 68 ff e5 85 68 fb 0c
%Jan 13 10:53:55 2009 ABC RM/5/RTLOG:
[OSPF LOG] 2009/01/13 10:53:55 - 246491
[OSPF] OSPF New Lsa:
00 01 20 03 85 69 a2 00 85 68 fb 02 80 00 00 01
92 3b 00 1c ff ff ff 80 00 00 00 73 85 68 fb 0c 
 
Handling Process
In an OSPF LSA packet in the format shown below, fields in the B part show the link state (LS) ID, that is, the route prefix, fields in the C part show the ID of the advertising router (Advertise ID), and fields in the F part show the subnet mask of this route prefix. You can obtain related information by translating the OSPF LSA packet into the decimal format:
AA AA AA AA BB BB BB BB CC CC CC CC DD DD DD DD
EE EE EE EE FF FF FF FF GG GG GG GG HH HH HH HH
The old LSA is 133.105.162.3 with subnet mask as 255.255.255.128. The IP address of the advertising router is 133.104.255.229
The new LAS is 133.105.162.0 with subnet mask as 255.255.255.128. The IP address of the advertising router is 133.104.251.2. 
 
Root Cause
The logs display packet information in hexadecimal format. Two pieces of LSA information are displayed on the router for each network: One is the old LSA information, represented by OSPF Old Lsa; the other is the new LSA information, represented by OSPF New Lsa.  
Suggestions
You can use this method to determine the router and route prefix at the faulty point for the purpose of further troubleshooting the problem.  

END