</p>四、故障现象描述
8 O& p- h' B/ ~: ]! ^" \7 B运营商反映:A市,B市和D市的流量全部中断,但C地市的业务都没有问题;问题出现时,出现故障的地市T128的缺省路由都指向了本市的核心交换机T64G。通过在三台ABR上添加默认路由指到骨干区域,故障得以恢复;经检查,C地市之所以没有出现故障是因为T128上配置了静态的默认路由;
4 n& ]8 F6 F: I, S8 @8 @1 H2 `五、处理方法
2 Q: X3 H5 R% }4 |1 r为什么出现问题时,作为ABR的NE80和T128,其默认路由会指到T64G?让我们先看一下做为ABR的T128以及T64G的配置是怎样的:5 y& U A/ b. U0 v6 h+ @" [
T64G:+ ] K5 }8 c' u* b8 T6 L& s7 O
# s) K+ ]6 R- Z6 X' m7 u% r, i: }
router ospf 11 }% E. e6 s+ J/ c! D
router-id 222.49.10.254
+ k! k! J. {, h3 F/ F% w4 o: ?network 222.49.10.132 0.0.0.3 area 0.0.3.28
- y( b! q: S! hnetwork 222.49.10.148 0.0.0.3 area 0.0.3.28, Q2 w9 R0 G& N! H
network 222.49.10.152 0.0.0.3 area 0.0.3.28
$ ]$ c& g* ~/ F- G5 A( b- Gnetwork 222.49.10.156 0.0.0.3 area 0.0.3.28( i% t) Z& k2 Y" L! c2 h; [/ w
network 222.49.10.254 0.0.0.0 area 0.0.3.28 n+ s9 z! F; n3 j2 G# A
area 0.0.3.28 authentication message-digest
! z' Q) v8 j7 n* k5 Oarea 0.0.3.28 nssa default-information-originate no-summary
/ X) Z* N( [6 I0 b, \//因特殊需要发布的缺省路由
! h% H) o; @0 C/ Wredistribute connected2 W! @% Q+ `% u3 B8 ~, s
redistribute static注:OSPF协议并没有规定NSSA内部路由器不能发布缺省路由' l: n. v( C4 y$ s8 |, E; w1 t
T128:% P" X6 D! T0 w5 N) W! W
2 I7 s) c8 Z9 q/ X) ~
; G1 S/ }5 A: ?8 o/ nT128-R1#sh run | be router ospf8 U q2 J1 b) v/ T% }, d+ C
Building configuration...$ H! J* _; Q ^4 G, ]
router ospf 11 K ?% S4 z" _
router-id 222.49.10.2504 r( W: K# C- `2 b
network 222.49.10.128 0.0.0.3 area 0.0.0.0
+ h0 }5 v W/ u7 znetwork 222.49.10.132 0.0.0.3 area 0.0.3.28$ h1 U: S* C# K, {4 o
network 222.49.10.136 0.0.0.3 area 0.0.3.28
! \. ?4 Z3 @+ V" Anetwork 222.49.10.250 0.0.0.0 area 0.0.0.01 ~9 J! ]4 S7 t
area 0.0.3.28 authentication message-digest+ }" c' P: x& D3 L3 Q
area 0.0.3.28 nssa default-information-originate no-summary
2 Y" F/ ?( [" Y8 ^3 [ //做为ABR向NSSA内部发布的缺省路由正常情况下,T128会学习骨干NE80发布的缺省路由,而不会学习T64G发布的缺省路由,那么故障发生时,最大的可能性就是NE80的缺省路由失效了:+ G# i) S/ O# g. I/ Z7 r
在故障恢复后,我们查看T128的database,发现了两条默认路由的LSA:
1 h; @) n" @6 ^ g0 n, ?7 D1 P; n$ {8 E3 I; U
Type-5 AS External Link States
$ e3 T' X; q7 Y. y* |LS age: 1493
8 i* ], X; C" U# X+ mOptions: (No TOS-capability, No DC)
. K2 b% c: v+ Z! t9 P) O8 [# PLS Type: AS External Link" d0 Z' w! `9 d; W& E. L
Link State ID: 0.0.0.0 (External Network Number)1 X2 T! a4 \8 h) b; f$ s* e; P
Advertising Router: 211.98.46.230 //经查证是核心NE80的loopback$ o/ ~, c$ K) ~
LS Seq Number: 0x80007154# U F! c7 J0 k0 }
Checksum: 0x1abd% c F3 Q3 ~& f# R7 }& M1 c* S
Length: 36
6 _! f( }% T" l U7 r3 M5 T9 uNetwork Mask: /03 b5 \/ n9 c- L: x( O
Metric Type: 2 (Larger than any link state path)
a) R- M8 {. R, @$ Y! U2 ?TOS: 0
, h) K4 m9 l- z3 q5 oMetric: 1000
; T, u: i. F' x- J8 qForward Address: 0.0.0.0
7 q0 e% w# o2 e! C. r) z
7 w" z! z' N: o3 bType-7 AS External Link States (Area 0.0.3.28), U; U" u* u, R% \9 \# w! J
LS age: 9687 f- ]! f- n3 H% @7 E- ]
Options: (No TOS-capability, No Type 7/5 translation, No DC)
_# d# ~3 X6 W, q! V rLS Type: AS External Link
7 o- x# y) k- x( V% |7 YLink State ID: 0.0.0.0 (External Network Number)
: _# a3 I# G, i0 V. B3 wAdvertising Router: 222.49.10.254//是NSSA内部的T64G
) M M, e2 R8 ?- ]( ] vLS Seq Number: 0x80002373; {. [8 ]% Z$ N: p
Checksum: 0x881a
8 ~" {' K5 y* C P. YLength: 36
5 F0 L" R7 ]6 z( F7 V% V INetwork Mask: /0- r- i) s+ n9 R; A
Metric Type: 2 (Larger than any link state path)9 r/ X+ \: D/ X4 C( p) R
TOS: 0! v% i2 b" `: Y
Metric: 1
( w/ c6 O Y3 g1 Z3 ZForward Address: 0.0.0.0 |