LSA 5和LSA 7的区别
LSA 5和LSA 7的区别
To provide the ability of carrying external routes originated in the NSSA, a new LSA type was defined, Type 7 LSA. It has the structure and semantics of a Type 5 (External) LSA, witha two differences:
1.Type 7 LSAs can be originated and propagated within the NSSA, they do not cross area borders like Type 5 LSAs do.
2.Type 5 LSAs are not supported in NSSA; they can be neither originated nor propagated in NSSA.
2.Type 5 LSAs are not supported in NSSA; they can be neither originated nor propagated in NSSA.
Translation of Type 7 to Type 5 LSA at the ABR
An ASBR in a NSSA injects its external routes as Type 7 LSAs (The NSSA does not support Type 5 Externals). The ABR can (optionally) translate those to regular Type 5 LSAs and inject them into the backbone as Type 5 Externals. At this point the these LSAs are indistinguishable from other Type 5 LSAs that may have come from other source. As shown on the figure below, these Type 5 LSAs, along with those from other sources, are flooded on all other non-stub areas.
When the NSSA is connected to the backbone via more than one ABR, the ABR with the highest Router ID is selected to perform the Type 7 à Type 5 translation. If that ABR fails, the ABR with next-highest Router ID is selected.
TYPE 7-->TYPE 5
应该举一个例子,把show ip ospf data里面的信息显示出来啦~
这个是在nssa区域上的abr上show的数据库信息
这个是在nssa区域上的abr上show的数据库信息
r2#sh ip ospf data
|
OSPF Router with ID (
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
2.2.2.2 2.2.2.2 437 0x80000003 0x3668 2 Summary Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
4.4.4.4 2.2.2.2 674 0x80000001 0x 4.4.4.4 151.1.1.1 1440 0x80000001 0xF35D 5.5.5.5 2.2.2.2 232 0x80000001 0xD441 5.5.5.5 151.1.1.1 1397 0x80000001 0xA7DB 192.168.13.0 1.1.1.1 1639 0x80000001 0xACD5 192.168.24.0 2.2.2.2 988 0x80000004 0xF61 192.168.24.0 151.1.1.1 1435 0x80000004 0xE1FB 192.168.25.0 2.2.2.2 236 0x80000007 0xDFC2 192.168.25.0 151.1.1.1 1401 0x80000003 0xBA59 Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
4.4.4.4 4.4.4.4 679 0x80000009 0x4FFE 3 Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
3.3.3.3 151.1.1.1 1474 0x80000001 0xA470 5.5.5.5 151.1.1.1 1398 0x80000001 0xA7DB 192.168.13.0 151.1.1.1 1541 0x80000001 0xE 192.168.25.0 151.1.1.1 1408 0x80000001 0xBE57 Router Link States (Area 3)
Link ID ADV Router Age Seq# Checksum Link count
5.5.5.5 5.5.5.5 241 0x80000008 0x Net Link States (Area 3)
Link ID ADV Router Age Seq# Checksum
192.168.25.2 Summary Net Link States (Area 3)
Link ID ADV Router Age Seq# Checksum
3.3.3.3 2.2.2.2 440 0x80000002 0x752B 3.3.3.3 151.1.1.1 1475 0x80000001 0xA470 4.4.4.4 2.2.2.2 440 0x80000002 0xC418 4.4.4.4 151.1.1.1 1441 0x80000001 0xF35D 192.168.12.0 2.2.2.2 440 0x80000005 0x373E 192.168.13.0 2.2.2.2 440 0x80000002 0xB482 192.168.13.0 151.1.1.1 1573 0x80000001 0xE 192.168.24.0 2.2.2.2 440 0x80000005 0xB2B6 192.168.24.0 151.1.1.1 1436 0x80000004 0xE1FB Type-7 AS External Link States (Area 3)
Link ID ADV Router Age Seq# Checksum Tag
25.25.24.0 55.55.55.0 5.5.5.5 238 0x80000003 0x5468 0 Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag 25.25.24.0 55.55.55.0 2.2.2.2 234 0x80000001 0x478D 0 |
注：在工程里面,通常为了减少路由表的深度,我们经常要在ABR上抑止LSA7到LSA5的转换,在以前有个小窍门,现在12.0 ios以后,直接就有命令可以抑止了。
