该文档测试,排错思路基于 ×××故障针断与排除第7章.AToM.
拓扑图:
在这里,R1到R3做AToM.
关键配置:R1和R4就是两台电脑:
R1 interface f0/0=1.1.1.1/24
R4 interface f0/0=1.1.1.2/24
R1做为PE-1-R1:
hostname PE-1-R2
ip cef
mpls label protocol ldp
interface Loopback0
ip address 10.1.1.1 255.255.255.255
!
interface FastEthernet0/0
no ip address
duplex full
speed auto
xconnect 10.1.1.3 100 encapsulation mpls
!
interface FastEthernet1/0
ip address 2.1.1.1 255.255.255.0
duplex full
speed auto
mpls label protocol ldp
mpls ip
!
router ospf 1
router-id 10.1.1.1
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 0
R2做为P-router:
hostname P-R3
ip cef
mpls label protocol ldp
!
interface Loopback0
ip address 10.1.1.2 255.255.255.255
!
interface FastEthernet0/0
ip address 2.1.1.2 255.255.255.0
duplex full
speed auto
mpls label protocol ldp
mpls ip
!
interface FastEthernet1/0
ip address 3.1.1.1 255.255.255.0
duplex full
speed auto
mpls label protocol ldp
mpls ip
!
router ospf 1
router-id 10.1.1.2
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 0
R3作为PE-2-R3:
hostname PE-2-R4
ip cef
mpls label protocol ldp
interface Loopback0
ip address 10.1.1.3 255.255.255.255
!
interface FastEthernet0/0
ip address 3.1.1.2 255.255.255.0
duplex full
speed auto
mpls label protocol ldp
mpls ip
!
interface FastEthernet1/0
no ip address
duplex full
speed auto
xconnect 10.1.1.1 100 encapsulation mpls
!
router ospf 1
router-id 10.1.1.3
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 0
好了,下面来说说troubleshooting的部分.如何才能快速定位一个AToM的问题所在.
关于MTU的问题.这个老身长谈的问题,今天又要拿来说一下了.从PC 1.1.1.1 ping 1.1.1.2 size 1500的话,肯定是ping 不通的.因为mpls接口的默认mtu是1500.这样还需要把标签8+4控制字+4字节的hdlc报文头减去,这样实际踩能通1500-16=1484.
我们可以看看默认的mpls 接口:
PE-1-R2#show mpls interfaces fastEthernet 1/0 detail
Interface FastEthernet1/0:
IP labeling enabled (ldp):
Interface config
LSP Tunnel labeling not enabled
BGP labeling not enabled
MPLS operational
MTU = 1540
PE-1-R2#
看到了吧,这里实际的mpls mtu=1500...等我们把mpls接口下面的mtu都改了就可以ping通了.
interface FastEthernet1/0
ip address 2.1.1.1 255.255.255.0
duplex full
speed auto
mpls mtu 1540
mpls label protocol ldp
mpls ip
end
PE-1-R2#show ip cef
Prefix Next Hop Interface
0.0.0.0/0 no route
0.0.0.0/8 drop
0.0.0.0/32 receive
2.1.1.0/24 attached FastEthernet1/0
2.1.1.0/32 receive FastEthernet1/0
2.1.1.1/32 receive FastEthernet1/0
2.1.1.2/32 attached FastEthernet1/0
2.1.1.255/32 receive FastEthernet1/0
3.1.1.0/24 2.1.1.2 FastEthernet1/0
10.1.1.1/32 receive Loopback0
10.1.1.2/32 2.1.1.2 FastEthernet1/0
10.1.1.3/32 2.1.1.2 FastEthernet1/0
127.0.0.0/8 drop
224.0.0.0/4 drop
224.0.0.0/24 receive
240.0.0.0/4 drop
255.255.255.255/32 receive
各台中心骨干网router的cef总要起起来吧,这个可是必要的..呵呵.
PE-1-R2#show mpls interfaces
Interface IP Tunnel BGP Static Operational
FastEthernet1/0 Yes (ldp) No No No Yes
PE-1-R2#
P-R3#show mpls interfaces
Interface IP Tunnel BGP Static Operational
FastEthernet0/0 Yes (ldp) No No No Yes
FastEthernet1/0 Yes (ldp) No No No Yes
P-R3#
看看每台骨干网router的mpls 是否开启在接口下面.
PE-1-R2#show mpls ldp discovery
Local LDP Identifier:
10.1.1.1:0
Discovery Sources:
Interfaces:
FastEthernet1/0 (ldp): xmit/recv
LDP Id: 10.1.1.2:0
Targeted Hellos:
10.1.1.1 -> 10.1.1.3 (ldp): active/passive, xmit/recv
LDP Id: 10.1.1.3:0
PE-1-R2#
这里可以看看ldp是否完成了收发.
还有一个是要确保,中间骨干网上面要允许UDP/TCP port=646 , multicast 224.0.0.2的报文通过,因为这个是ldp建立邻居的hello报文需要的端口号.
否则的话会被ip access list 最后一句隐藏的deny any any而建立不起邻居.
PE-1-R2#show mpls ldp neighbor
Peer LDP Ident: 10.1.1.3:0; Local LDP Ident 10.1.1.1:0
TCP connection: 10.1.1.3.62425 - 10.1.1.1.646
State: Oper; Msgs sent/rcvd: 82/80; Downstream
Up time: 00:59:08
LDP discovery sources:
Targeted Hello 10.1.1.1 -> 10.1.1.3, active, passive
Addresses bound to peer LDP Ident:
3.1.1.2 10.1.1.3
Peer LDP Ident: 10.1.1.2:0; Local LDP Ident 10.1.1.1:0
TCP connection: 10.1.1.2.51161 - 10.1.1.1.646
State: Oper; Msgs sent/rcvd: 17/18; Downstream
Up time: 00:08:50
LDP discovery sources:
FastEthernet1/0, Src IP addr: 2.1.1.2
Addresses bound to peer LDP Ident:
2.1.1.2 3.1.1.1 10.1.1.2
PE-1-R2#
所以,ldp邻居有直连的.还有对端PE的,这就是两种LDP邻居.
最后就是比较重量级的了:
PE-1-R2#show mpls l2transport vc vcid 100 detail
Local interface: Fa0/0 up, line protocol up, Ethernet up
Destination address: 10.1.1.3, VC ID: 100, VC status: up
Output interface: Fa1/0, imposed label stack {18 20}
Preferred path: not configured
Default path: active
Next hop: 2.1.1.2
Create time: 01:03:32, last status change time: 00:23:40
Signaling protocol: LDP, peer 10.1.1.3:0 up
MPLS VC labels: local 20, remote 20
Group ID: local 0, remote 0
MTU: local 1500, remote 1500 //看mtu是多少
Remote interface description:
Sequencing: receive disabled, send disabled
VC statistics:
packet totals: receive 1536, send 1549
byte totals: receive 542617, send 585294
packet drops: receive 0, seq error 0, send 28
PE-1-R2#
你想比较一下两边是否vcid一样,附属接口状态如何,
PE-1-R2#show mpls l2transport vc
Local intf Local circuit Dest address VC ID Status
------------- -------------------------- --------------- ---------- ----------
Fa0/0 Ethernet 10.1.1.3 100 UP
PE-1-R2#
PE-2-R4#show mpls l2transport vc
Local intf Local circuit Dest address VC ID Status
------------- -------------------------- --------------- ---------- ----------
Fa1/0 Ethernet 10.1.1.1 100 UP
PE-2-R4#
这个表也就是当前L2 AToM的状态表了.
总结:
注意,在使用的时候,类型一定要一致的.还有就是vcID需要一致.而且附属端口的状态是要up的.路由就不说了.这个是基础,CEF快速转发表要打开.全局下面要起mpls ip,然后标签分发协议要用ldp的,因为cisco默认的是tdp的,在xconnect附属接口上,vcid两边要相同,两边的接口类型也需要一致。不能本端是ppp,对端是HDLC的. 还有就是,中间骨干网上面,一定要保证UDP/TCP port=646的端口,224.0.0.2的组播过,因为那是ldp建立邻居时候需要的端口号.只要注意了这些,AToM应该也不是什么难事了.
上面所有ciscoIOS版本为:
Cisco IOS Software, 7200 Software (C7200-ADVIPSERVICESK9-M), Version 12.4(24)T, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Thu 26-Feb-09 00:31 by prod_rel_team