思科BGP不等成本负载平衡

9

我正在尝试在我的网络中实现BGP不等成本负载平衡功能。根据思科手册（long：http : //www.cisco.com/c/en/us/td/docs/ios/12_2s/feature/guide/fsbgplb.html，简称：https : //ccieblog.co.uk / bgp / bgp-unqual-load-cost-sharing），我已经建立了这样的网络拓扑：

网络拓扑

R1-我正在尝试为传出流量实现负载平衡的路由器。使用名称nat为VRF的表。

R2- R4-运行quagga的NAT服务器，默认路由到R5通过eBGP 与R1共享。

R1配置

R1 IOS版本： 12.2（33）SXJ4（s72033-adventerprisek9_wan-mz.122-33.SXJ4.bin）

R2配置（仅R3 R4的 router-id和vlan不同）

结果，我在R1上拥有3个不同的默认路由，共享计数为1/1（1：1：1）。但是比例1：2：3扩大了：

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

我究竟做错了什么？根据手册，不同的dmzlink bw值应导致不同的负载分配比例，但实际上-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 ip bgp邻居输出

R1# sh run

R1运行配置 敏感信息被屏蔽

cisco  load-balancing  bgp 
— 萨曼奴4
source
1
R1的运行配置是否丢失bandwidth 50000了“接口Vlan3228”？您还可以附加“ sh ip bgp <R5的IP>”的输出吗？
— Andrey Sapegin
1
同样在运行配置中，据我了解，带宽应为50kbs-100kbs-150kbs，并且您的输出R1# sh ip bgp vpnv4 vrf nat 0.0.0.0显示为125kbs-250kbs-350kbs ...
— Andrey Sapegin
1
@AndreySapegin sh ip bgp vpnv4 vrf nat 10.30.228.228显示与相同sh ip bgp vpnv4 vrf nat 0.0.0.0。您错过了neighbors关键字吗？如果是这样，sh ip bgp vpnv4 vrf nat neighbors 10.30.228.228您的输出可以在R1
— Shamanu4
1
您提到的指南（cisco.com/c/en/us/td/docs/ios/12_2s/feature/guide/fsbgplb.html）区分neighbor dmzlink-bw，这仅允许向邻居（在您的配置中显示）发布带宽bgp dmzlink-bw。这将实现比例负载均衡（在您的配置中似乎缺少）。您可以尝试放入bgp dmzlink-bw正在运行的配置吗？
— Andrey Sapegin 2015年
1
@AndreySapegin。是的，我确定maximum paths应该在address-family。我在vrf实例中需要多路径功能，但在全局路由表中不需要。如果放到maximum paths下面，router bgp 100我只会得到一条通过R5的路线，而没有一条通过R3和R2的路线。对于ibgp地址不足的家庭，结果相同，因为所有邻居都是外部的。端口通道上的带宽继承在配置中是一致的。我删除了这行没有任何效果。提交
— Shamanu4

Answers:

3

关键问题似乎是bgp dmzlink-bw配置中地址族下缺少的选项。但是，让我在这里总结一下我的意见：

  1. bgp dmzlink-bw在address-family。neighbor dmzlink-bw仅启用向邻居通告带宽，而bgp dmzlink-bw本身启用比例负载均衡。
  2. Running-config bandwidth 50000的“接口Vlan3228”缺少选项
  3. 如本配置示例所述，maximum-paths eibgp 3可能需要选项而不是maximum-paths 3
  4. 除了sh ip bgp vpnv4 vrf nat 0.0.0.0Shamanu4和bangal所著的原始指南中提到的命令以及其他命令（请参阅问题）外，检查使用以下方式进行负载平衡的链路的流量共享计数是否有所不同也很有用：sh ip route vrf nat 0.0.0.0
  5. 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，当您有一个包含许多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，我将使用空的配置创建一个类似的设置，并尝试在那里仅配置相关选项（“最小工作示例”），以查看其是否有效并且不干扰其他选项，访问列表（仅作为示例，如果您没有备用硬件，并且您的路由器已经投入生产，因此您不能直接在其上进行空配置试验，则可以：

  • 将Linux PC / VM与Quagga等路由软件一起使用（问题中提到）
  • 使用来自Cisco的模拟器：用于CCNP的Boson NetSim支持BGP，但是我不确定是否支持地址族/ VPN / VRF
  • 将虚拟机与Cisco的IOS XRv一起使用。据我所知，它是免费提供的，带宽限制为2 Mbit / s，足以进行测试。同样，我不确定是否支持地址族/ 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。有适用于它的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这样的地方尽可能便宜地购买二手硬件，仅用于测试目的。
— 安德烈·萨佩金（Andrey Sapegin）
source
1
仍无法证实或反驳这一理论。IOS版本15.1（2）SY4a也没有dmzlink-bw位于下的选项address-family。我需要一些时间来解决cisco docs与现实生活中的矛盾。
— Shamanu4
真的很奇怪 你可以尝试看看下面的文档：cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/...，cisco.com/c/en/us/td/docs/ios -xml / ios / iproute_bgp / configuration /…，但我看不到您的配置中缺少任何内容...
— Andrey Sapegin 2015年
我将购买cisco VIRL许可证并尝试在那里模拟拓扑。我将在稍后的发布中报告任何结果。感谢帮助。
— Shamanu4
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