MPLS Aggreate & Untag
aggregate 与 untag :
PE1#sh ip route vrf ihgazni
Routing Table: ihgazni
10.0.0.0/24 is subnetted, 1 subnets
C 10.0.0.0 is directly connected, Serial1/0
11.0.0.0/32 is subnetted, 1 subnets
D 11.11.11.11 [90/2297856] via 10.0.0.11, 00:02:12, Serial1/0
PE1#sh mpls for
Local Outgoing Prefix Bytes tag Outgoing Next Hop
17 Aggregate 10.0.0.0/24[V] 0
18 Untagged 11.11.11.11/32[V] 0 Se1/0 point2point
PE1#sh mpls for de
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
17 Aggregate 10.0.0.0/24[V] 0
MAC/Encaps=0/0, MRU=0, Tag Stack{}
VPN route: ihgazni
No output feature configured----------vrf 直连接口
Per-packet load-sharing
18 Untagged 11.11.11.11/32[V] 0 Se1/0 point2point
MAC/Encaps=0/0, MRU=1504, Tag Stack{}
VPN route: ihgazni
No output feature configured
Per-packet load-sharing------------通过vrf 接口从CE路由器学来的路由
PE1#sh ip bgp vpnv4 all
BGP table version is 29, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 11:11 (default for vrf ihgazni)
*> 10.0.0.0/24 0.0.0.0 0 32768 ?
*> 11.11.11.11/32 10.0.0.11 2297856 32768 ?
PE1#sh ip bgp vpnv4 all 10.0.0.0 255.255.255.0
BGP routing table entry for 11:11:10.0.0.0/24, version 10
Paths: (1 available, best #1, table ihgazni)
Flag: 0x820
Advertised to update-groups:
1
Local
0.0.0.0 from 0.0.0.0 (1.1.1.1)
Origin incomplete, metric 0, localpref 100, weight 32768, valid, sourced,
best
Extended Community: SoO:1111:1111 RT:11:11
Cost:pre-bestpath:128:2169856 (default-2145313791) 0x8800:32768:0
0x8801:10:512000 0x8802:65280:1657856 0x8803:65281:1500
mpls labels in/out 17/aggregate(ihgazni)
PE1#
PE1#sh ip bgp vpnv4 all 11.11.11.11 255.255.255.255
BGP routing table entry for 11:11:11.11.11.11/32, version 11
Paths: (1 available, best #1, table ihgazni)
Flag: 0x820
Advertised to update-groups:
1
Local
10.0.0.11 from 0.0.0.0 (1.1.1.1)
Origin incomplete, metric 2297856, localpref 100, weight 32768, valid, sou
rced, best
Extended Community: SoO:1111:1111 RT:11:11
Cost:pre-bestpath:128:2297856 (default-2145185791) 0x8800:32768:0
0x8801:10:640000 0x8802:65281:1657856 0x8803:65281:1500
mpls labels in/out 18/nolabel
PE1#
PE1#sh mpls ldp binding
tib entry: 1.1.1.1/32, rev 4
local binding: tag: imp-null
remote binding: tsr: 2.2.2.2:0, tag: 16
tib entry: 2.2.2.2/32, rev 6
local binding: tag: 16
remote binding: tsr: 2.2.2.2:0, tag: imp-null
tib entry: 12.0.0.0/24, rev 2
local binding: tag: imp-null
remote binding: tsr: 2.2.2.2:0, tag: imp-null
PE1#
PE1#sh ip cef vrf ihgazni
Prefix Next Hop Interface
0.0.0.0/0 drop Null0 (default route handler entry)
0.0.0.0/32 receive
10.0.0.0/24 attached Serial1/0
10.0.0.0/32 receive
10.0.0.1/32 receive
10.0.0.255/32 receive
--------------------------------------------
11.11.11.11/32 10.0.0.11 Serial1/0
------------------有下一跳与接口的绑定
20.0.0.0/24 12.0.0.2 Serial1/2
22.0.0.0/24 12.0.0.2 Serial1/2
22.22.22.22/32 12.0.0.2 Serial1/2
50.50.50.50/32 12.0.0.2 Serial1/2
60.60.60.60/32 12.0.0.2 Serial1/2
200.200.200.200/32 12.0.0.2 Serial1/2
224.0.0.0/4 drop
224.0.0.0/24 receive
255.255.255.255/32 receive
PE1#
10.0.0.0/24, version 5, epoch 0, attached, connected, cached adjacency to Serial1/0
0 packets, 0 bytes
tag information set
local tag: 17
via Serial1/0, 0 dependencies
valid cached adjacency
tag rewrite with , , tags imposed: {}
10.0.0.0/32, version 7, epoch 0, receive
10.0.0.1/32, version 6, epoch 0, receive
10.0.0.255/32, version 8, epoch 0, receive
11.11.11.11/32, version 26, epoch 0, cached adjacency to Serial1/0
0 packets, 0 bytes
tag information set
local tag: 18
via 10.0.0.11, Serial1/0, 0 dependencies
next hop 10.0.0.11, Serial1/0----------有下一跳和接口的绑定
valid cached adjacency
tag rewrite with Se1/0, point2point, tags imposed: {}
========================
那为身么直连的prefix 要标成aggregate :需要3层IP 查找
而从CE学来的prefix 直接就从CEF 转发了呢?直连的再进行3层查找，最终还要从那个接口出去，不是多此一举么?
因为CEF要把下一跳和2层进行对应才能有adjancy。CE学来的prefix，有下一跳，下一跳就是CE 的接口，所以就能确定对应的2层信息（ARP 找网挂CE，或者点对点找HDLC或者找DLCI）。而直连的，没有下一跳，下一跳是随包的目地地址变化的,所以此类的
要标为aggregate.
aggregate的都是不能确定下一跳，从而不能确定LAYER 2的information.
POP 删除MPLS报文的最外层MPLS标签，并把该报文直接转发到下一个LSR
Untag 删除MPLS所有标签，并把该IP报文直接转发到下一跳路由器
Aggreate 删除MPLS所有标签，查找IP路由表，并把该报文转发到下一跳路由器
pop:弹掉一层标签后，不管现在的数据包上还有没有标签，继续往下一出口转发。
untag：把标签弹光，把数据包从接口发出去。
//上面二个都是不查路由表的。
aggregate:根据标签查找LFIB，确定是哪个VRF。再在这个VRF里的CEF表里进行一次路由查找。
