内网服务器----MSR56(IRF)----外网终端
两台MSR5660做了IRF堆叠作为某局点的出口设备,外网接口为G1/2/0/0和G2/2/0/0,在接口下配置了NAT server,内网接口为静态聚合口,该聚合口对接内网防火墙,由于防火墙接口做的是冗余,所以路由器静态聚合口接口下配置了link-aggregation selected-port maxumum 1
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interface GigabitEthernet1/2/0/0
port link-mode route description CUCC
bandwidth 200000
combo enable copper
ip address 221.7.XXX.XXX 255.255.255.240
ip last-hop hold
nat outbound 3000
nat server protocol tcp global current-interface 20211 inside 10.13.XXX.XXX 20211
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interface GigabitEthernet2/2/0/0
port link-mode route description CMCC
bandwidth 200000
combo enable copper
ip address 36.136.XXX.XXX 255.255.255.192
ip last-hop hold
nat outbound 3000
nat server protocol tcp global current-interface 20211 inside 10.13.XXX.XXX 20211
#
interface Route-Aggregation4
description TO-F1000
service chassis 1 slot 2
service standby chassis 2 slot 2
ip address 10.13.XXX.XXX 255.255.255.252
ospf network-type p2p
link-aggregation selected-port maximum 1
tcp mss 1280
qos apply policy ADWAN-QPInRAGG4 inbound
nat hairpin enable
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session synchronization enable
session synchronization dns http
现场二框在映射的时候发现NAT设备上是存在相应的nat会话的,这说明入方向的映射过程没问题,但是后续的回程报文可能在某个环节丢弃了。通过debug ip packet 可以看到报文交互的过程。看到报文在回到内网聚合口的时候因为FIB BLACKHOLE丢弃了。推测是由于内网聚合口只选中了1框,所以二框的映射报文前往内网服务器需要走一框,同时回程报文也是回到1框,因为缺省路由走的一框,从一框出口出去但是没找到会话,所以报文丢弃。在上述组网和配置下可能IRF会话同步和ip last-hop hold未生效。
*Dec 31 15:27:32:408 2021 NNYY_04FDCRT03101 IPFW/7/IPFW_PACKET: -Chassis=1-Slot=2;
Discarding, interface = ifIndex:10881
version = 4, headlen = 20, tos = 0
pktlen = 52, pktid = 54339, offset = 0, ttl = 251, protocol = 6
checksum = 6939, s = 10.13.XXX.XXX, d = 183.242.XXX.XXX
channelID = 0, vpn-InstanceIn = 0, vpn-InstanceOut = 0.
prompt: Special outgoing interface FIB BLACKHOLE.
Payload: TCP
source port = 20211, destination port = 14662
sequence num = 0x3029b259, acknowledgement num = 0x67ee4ec3, flags = 0x12
window size = 65535, checksum = 0x7e39, header length = 32.
上述案例中的问题:
1、外网接口是以太口,并非全局口,这种情况下会话同步功能不生效。可以将设备外网接口的配置移到聚合口下,如: 新建两个聚合口,现场的2/2/0/0 放在聚合口A,1/2/0/0放在聚合口B ,将以太口下的配置复制到相应聚合口下。
2、Ip last-hop hold enable 针对于同框非跨板转发场景,对于跨框需求还需要在全局下配置 ip last-hop backup enable
3、缺少会话热备配置
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