我正在尝试在我的网络中实现 BGP 不等价负载平衡功能。根据思科手册（长：http://www.cisco.com/c/en/us/td/docs/ios/12_2s/feature/guide/fsbgplb.html， 短的：https://ccieblog.co.uk/bgp/bgp-unequal-load-cost-sharing）我建立了这样的网络拓扑：
R1- 我试图实现传出流量负载平衡的路由器。nat使用带名称的 VRF 表。
R2-R4- 运行 quagga 的 NAT 服务器，默认路由到R5和...分享R1通过 eBGP。
R1 IOS版本：12.2(33)SXJ4 (s72033-adventerprisek9_wan-mz.122-33.SXJ4.bin)
R2 配置（R3 R4只有 router-id 和 vlan 不同)
因此，我有 3 条不同的默认路由R1份额数相同 - 1/1 (1:1:1)。但比例 1:2:3 预期：
R1# sh ip bgp vpnv4 vrf nat 0.0.0.0
Paths: (6 available, best #5, table nat)
Multipath: eiBGP
Advertised to update-groups:
2
65000
10.30.227.227 from 10.30.227.227 (10.30.227.227)
Origin IGP, localpref 100, valid, external, multipath
Extended Community: RT:192.168.33.4:13
DMZ-Link Bw 250 kbytes
65000, (received-only)
10.30.227.227 from 10.30.227.227 (10.30.227.227)
Origin IGP, localpref 100, valid, external
DMZ-Link Bw 250 kbytes
65000
10.30.228.228 from 10.30.228.228 (10.30.228.228)
Origin IGP, localpref 100, valid, external, multipath
Extended Community: RT:192.168.33.4:13
DMZ-Link Bw 375 kbytes
65000, (received-only)
10.30.228.228 from 10.30.228.228 (10.30.228.228)
Origin IGP, localpref 100, valid, external
DMZ-Link Bw 375 kbytes
65000
10.30.225.225 from 10.30.225.225 (10.30.225.225)
Origin IGP, localpref 100, valid, external, multipath, best
Extended Community: RT:192.168.33.4:13
DMZ-Link Bw 125 kbytes
65000, (received-only)
10.30.225.225 from 10.30.225.225 (10.30.225.225)
Origin IGP, localpref 100, valid, external
DMZ-Link Bw 125 kbytes
R1# sh ip cef vrf nat 0.0.0.0/0 internal
0.0.0.0/0, epoch 3, flags rib only nolabel, rib defined all labels, RIB[B], refcount 7, per-destination sharing
sources: RIB, D/N, DRH
feature space:
NetFlow: Origin AS 0, Peer AS 0, Mask Bits 0
Broker: linked
IPRM: 0x00018000
subblocks:
DefNet source: 0.0.0.0/0
ifnums:
Vlan3225(231): 10.30.225.225
Vlan3227(232): 10.30.227.227
Vlan3228(233): 10.30.228.228
path 541B7858, path list 53E3E0D8, share 1/1, type recursive nexthop, for IPv4, flags resolved
recursive via 10.30.225.225[IPv4:nat], fib 5496C804, 1 terminal fib
path 541B7BF8, path list 53E3E170, share 1/1, type adjacency prefix, for IPv4
attached to Vlan3225, adjacency IP adj out of Vlan3225, addr 10.30.225.225 513F6B60
path 541B78CC, path list 53E3E0D8, share 1/1, type recursive nexthop, for IPv4, flags resolved
recursive via 10.30.227.227[IPv4:nat], fib 54969B7C, 1 terminal fib
path 541B7B10, path list 53E3E08C, share 1/1, type adjacency prefix, for IPv4
attached to Vlan3227, adjacency IP adj out of Vlan3227, addr 10.30.227.227 513F66E0
path 541B7DC8, path list 53E3E0D8, share 1/1, type recursive nexthop, for IPv4, flags resolved
recursive via 10.30.228.228[IPv4:nat], fib 54970EAC, 1 terminal fib
path 541B79B4, path list 53E3E040, share 1/1, type adjacency prefix, for IPv4
attached to Vlan3228, adjacency IP adj out of Vlan3228, addr 10.30.228.228 513F6560
output chain:
loadinfo 51283B80, per-session, 3 choices, flags 0003, 5 locks
flags: Per-session, for-rx-IPv4
15 hash buckets
< 0 > IP adj out of Vlan3225, addr 10.30.225.225 513F6B60
< 1 > IP adj out of Vlan3227, addr 10.30.227.227 513F66E0
< 2 > IP adj out of Vlan3228, addr 10.30.228.228 513F6560
< 3 > IP adj out of Vlan3225, addr 10.30.225.225 513F6B60
< 4 > IP adj out of Vlan3227, addr 10.30.227.227 513F66E0
< 5 > IP adj out of Vlan3228, addr 10.30.228.228 513F6560
< 6 > IP adj out of Vlan3225, addr 10.30.225.225 513F6B60
< 7 > IP adj out of Vlan3227, addr 10.30.227.227 513F66E0
< 8 > IP adj out of Vlan3228, addr 10.30.228.228 513F6560
< 9 > IP adj out of Vlan3225, addr 10.30.225.225 513F6B60
<10 > IP adj out of Vlan3227, addr 10.30.227.227 513F66E0
<11 > IP adj out of Vlan3228, addr 10.30.228.228 513F6560
<12 > IP adj out of Vlan3225, addr 10.30.225.225 513F6B60
<13 > IP adj out of Vlan3227, addr 10.30.227.227 513F66E0
<14 > IP adj out of Vlan3228, addr 10.30.228.228 513F6560
Subblocks:
None
我做错了什么？根据手册，不同的dmzlink bw值应该会导致不同的负载分担比例，但事实上 - 事实并非如此！
更新 1 — 由用户 bangal 请求
R1# show ip bgp all summary
For address family: IPv4 Unicast
BGP router identifier X.X.X.129, local AS number 41096
BGP table version is 22283352, main routing table version 22283352
34749 network entries using 4065633 bytes of memory
61661 path entries using 3206372 bytes of memory
8119/5337 BGP path/bestpath attribute entries using 1299040 bytes of memory
3752 BGP AS-PATH entries using 155474 bytes of memory
2990 BGP community entries using 138266 bytes of memory
146 BGP extended community entries using 5168 bytes of memory
53 BGP route-map cache entries using 1696 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 8871649 total bytes of memory
BGP activity 4716897/4682147 prefixes, 11331539/11269872 paths, scan interval 60 secs
# Here are bgp neighbours from global routing table. Not relevant to the question. IP addresses are hidden
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
X.X.X.1 4 XX219 791704 760380 22283352 0 0 6d17h 1
X.X.X.33 4 XX219 112902498 1315655 22283352 0 0 6d17h 0
X.X.X.238 4 XX772 801422 762830 22283352 0 0 2w5d 0
X.X.X.206 4 XX540 2886112 1313917 22283352 0 0 4w4d 9641
X.X.X.70 4 XX772 188343075 1313853 22283352 0 0 6d14h 25881
X.X.X.78 4 XX772 148265282 941127 22283352 0 0 2w6d 26098
# Here are neighbours for vrf nat.
For address family: VPNv4 Unicast
BGP router identifier X.X.X.129, local AS number 41096
BGP table version is 824, main routing table version 824
1 network entries using 137 bytes of memory
6 path entries using 408 bytes of memory
1 multipath network entries and 3 multipath paths
8119/1 BGP path/bestpath attribute entries using 1299040 bytes of memory
3752 BGP AS-PATH entries using 155474 bytes of memory
2990 BGP community entries using 138266 bytes of memory
146 BGP extended community entries using 5168 bytes of memory
53 BGP route-map cache entries using 1696 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 1600189 total bytes of memory
3 received paths for inbound soft reconfiguration
BGP activity 4716897/4682147 prefixes, 11331539/11269872 paths, scan interval 15 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.30.225.225 4 65000 11003 11443 824 0 0 3d18h 1
10.30.227.227 4 65000 9853 10293 824 0 0 3d18h 1
10.30.228.228 4 65000 10992 11432 824 0 0 3d18h 1
R1# sh ip route vrf nat
Routing Table: nat
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.30.228.228 to network 0.0.0.0
10.0.0.0/24 is subnetted, 4 subnets
C 10.30.0.0 is directly connected, Vlan30
C 10.30.228.0 is directly connected, Vlan3228
C 10.30.227.0 is directly connected, Vlan3227
C 10.30.225.0 is directly connected, Vlan3225
B* 0.0.0.0/0 [20/0] via 10.30.228.228, 3d18h
[20/0] via 10.30.227.227, 3d18h
[20/0] via 10.30.225.225, 3d18h
R1# sh ip bgp vpnv4 vrf nat neighbors
R1# sh run
R1 运行配置 敏感信息被屏蔽
答案1
关键问题似乎是bgp dmzlink-bw配置中地址系列下缺少一个选项。不过，让我在这里总结一下我的意见：
bgp dmzlink-bw下address-family仅neighbor dmzlink-bw允许向邻居通告带宽，而bgp dmzlink-bw自身则允许比例负载平衡。- 运行配置
bandwidth 50000缺少“接口 Vlan3228”选项 - 正如所提到的此配置示例，
maximum-paths eibgp 3可能需要选项，而不是maximum-paths 3 sh ip bgp vpnv4 vrf nat 0.0.0.0除了Shamanu4 和 bangal 的原始指南（参见问题）中提到的其他命令外，检查使用以下方法进行负载平衡的链接的流量份额计数是否不同也很有用sh ip route vrf nat 0.0.0.0- 检查是否没有其他选项可能会干扰负载平衡的配置（例如，
bandwidth inherit在端口通道上）
作为一般建议，当您拥有包含大量选项的大型运行配置时，有时很难识别问题。如果问题仍然存在，我会创建一个具有空配置的类似设置，然后尝试配置仅有的相关选项（最小工作示例），看看它是否有效并且不会干扰其他选项、访问列表（仅作为示例，在这种特殊情况下极不可能）等。如果您没有备用硬件，并且您的路由器正在生产中，因此您无法直接在其上尝试空配置，您可以：
- 使用 Linux PC/VM 和路由软件，如 Quagga（问题中提到）
- 使用思科的模拟器：CCNP 的 Boson NetSim支持 BGP，但我不确定是否支持地址系列/VPN/VRF
- 使用思科的 IOS XRv 虚拟机。据我所知，它是免费提供的，带宽限制为 2 Mbit/s，这应该足够进行测试了。同样，我不确定是否支持地址系列/VPN/VRF：Cisco IOS XRv 路由器概述，VM 下载链接
- 使用 GNS3 (http://www.gns3.com/) 模拟器。有它的 Cisco IOS 映像，但是我不知道如何获取它们。
- 最后，您甚至可以尝试从 ebay 等网站以尽可能便宜的价格购买二手硬件，仅用于测试目的。