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问Juniper系列iBGP路由的问题
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Network Engineering用户

提问于 2018-10-30 02:13:21

回答 2查看 661关注 0票数 6

我有一个简单的设置：

2x Juniper MX系列路由器，每个路由器都有一个到传输提供商的上行链路
两个路由器之间的iBGP会话(点到点)
出于测试目的，我已经禁用了从R2到传输提供者的上行链路。所有路由都是从R1 iBGP会话接收的。
试图找出为什么R2不能利用R1's路由，而它似乎有这样的路线

配置非常基本：

protocols {
    bgp {
        group internal-peers {
            type internal;
            description "iBGP between R1 and R2";
            local-address 172.16.20.1; # lo0.0
            export iBGP-send-direct;
            neighbor 172.16.20.2; # R2 lo0.0
        }
    }
    ospf {
        area 0.0.0.0 {
            interface lo0.0 {
                passive;
            }
            interface et-0/0/0.0; # point-to-point to R2
        }
    }
}

protocols {                             
    bgp {
        group internal-peers {
            type internal;
            description "iBGP between R2 and R1";
            local-address 172.16.20.2; # lo0.0
            export iBGP-send-direct;
            neighbor 172.16.20.1; # R1 lo0.0
        }
    }
    ospf {
        area 0.0.0.0 {
            interface lo0.0 {
                passive;
            }
            interface et-0/0/0.0; # point-to-point to R1
        }
    }
}

iBGP-发送-直接策略-声明

policy-statement iBGP-send-direct {     
    term 1 {                            
        from protocol direct;           
        then accept;                    
    }                                   
    term 2 {                            
        from protocol static;           
        then accept;                    
    }                                   
}

不过，当交通从R2到R1时，我得到了正确的路线，但它并没有到达上游：

user@r2> show route 1.1.1.1 

inet.0: 713294 destinations, 713297 routes (713294 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.0/24         *[BGP/170] 00:07:47, MED 2020, localpref 100, from 172.16.20.1
                      AS path: 174 13335 I, validation-state: unverified
                    > to 172.16.25.1 via et-0/0/0.0

当从R2跟踪1.1.1.1时，它将转到172.16.25.1 (这是可以到达的)，但是没有其他任何东西。R1上有一条1.1.1.1的路径。

user@r1> show route 1.1.1.1 

inet.0: 713326 destinations, 713329 routes (713326 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.0/24         *[BGP/170] 04:07:16, MED 2020, localpref 100
                      AS path: 174 13335 I, validation-state: unverified
                    > to 38.104.XX.XX via xe-0/1/4.0

我显然错过了一些很明显的东西。有人能说出一些见解吗？

谢谢。

routing

bgp

juniper

juniper-junos

juniper-mx

回答 2

Network Engineering用户

发布于 2018-11-01 20:02:39

为了感兴趣，我构建了一个测试拓扑，它显示在下面的图像中：

注意:所有路由器的信任几乎都是默认的。我所做的：

返回1.1.1.1/32的ISP路由器。通过BGP宣布1.1.1.0/24号路线至vMX-1。BGP会话到vMX-2没有配置；
vMX-1和vMX-2通过VRRP共享虚拟IP 198.18.100.3，该IP被设置为PC1的默认网关(198.18.100.5)；
vMX-1向ISP宣布198.18.100.0/24；
从vMX-2到ISP的连接故意删除。

路由器配置：

ISP

interface Loopback0
 ip address 1.1.1.1 255.255.255.255
!
interface FastEthernet0/0
 ip address 201.100.0.5 255.255.255.248
 duplex auto
 speed auto
!
router bgp 200
 no synchronization
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 201.100.0.1 remote-as 100
 neighbor 201.100.0.1 update-source FastEthernet0/0
 no auto-summary
!
ip route 1.1.1.0 255.255.255.0 Null0

状态：

Neighbor        V          AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
201.100.0.1     4        100      53      50        4    0    0 00:15:01        1

     1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C       1.1.1.1/32 is directly connected, Loopback0
S       1.1.1.0/24 is directly connected, Null0
     201.100.0.0/29 is subnetted, 1 subnets
C       201.100.0.0 is directly connected, FastEthernet0/0
B    198.18.100.0/24 [20/0] via 201.100.0.1, 00:07:38

vMX-1

interfaces {
    ge-0/0/0 {
        unit 0 {
            family inet {
                address 201.100.0.1/29;
            }
        }
    }
    ge-0/0/1 {
        unit 0 {
            family inet {
                address 172.16.25.1/30;
                address 198.18.100.1/29 {
                    vrrp-group 1 {
                        virtual-address 198.18.100.3;
                        priority 50;
                        accept-data;
                    }
                }
            }
        }
    }
    lo0 {
        unit 0 {
            family inet {
                address 172.16.20.1/32;
            }
        }
    }
}
routing-options {
    static {
        route 198.18.100.0/24 {
            discard;
            preference 240;
        }
    }
}
protocols {
    bgp {
        local-as 100;
        group internal-peers {
            type internal;
            local-address 172.16.20.1;
            export ibgp-local-as;
            neighbor 172.16.20.2;
        }
        group isp {
            type external;
            export bgp-local-as;
            neighbor 201.100.0.5 {
                peer-as 200;
            }
        }
    }
    ospf {
        area 0.0.0.0 {
            interface lo0.0 {
                passive;
            }
            interface ge-0/0/1.0;
        }
    }
}
policy-options {
    policy-statement bgp-local-as {
        term t1 {
            from {
                route-filter 198.18.100.0/24 exact;
            }
            then accept;
        }
    }
    policy-statement ibgp-local-as {
        term t1 {
            then {
                next-hop self;
            }
        }
    }
}

状态：

> show bgp summary
Table          Tot Paths  Act Paths Suppressed    History Damp State    Pending
inet.0
                       1          1          0          0          0          0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
172.16.20.2             100         42         44       0       0       18:28 0/0/0/0              0/0/0/0
201.100.0.5             200         36         41       0       0       17:09 1/1/1/0              0/0/0/0

> show route
inet.0: 12 destinations, 12 routes (12 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.0/24         *[BGP/170] 00:17:35, MED 0, localpref 100
                      AS path: 200 I, validation-state: unverified
                    > to 201.100.0.5 via ge-0/0/0.0
172.16.20.1/32     *[Direct/0] 00:32:40
                    > via lo0.0
172.16.20.2/32     *[OSPF/10] 00:21:16, metric 1
                    > to 172.16.25.2 via ge-0/0/1.0
                      to 198.18.100.2 via ge-0/0/1.0
172.16.25.0/30     *[Direct/0] 00:22:00
                    > via ge-0/0/1.0
172.16.25.1/32     *[Local/0] 00:22:00
                      Local via ge-0/0/1.0
198.18.100.0/24    *[Static/240] 00:09:57
                      Discard
198.18.100.0/29    *[Direct/0] 00:29:46
                    > via ge-0/0/1.0
198.18.100.1/32    *[Local/0] 00:29:46
                      Local via ge-0/0/1.0
198.18.100.3/32    *[Local/0] 00:22:42
                      Local via ge-0/0/1.0
201.100.0.0/29     *[Direct/0] 00:38:10
                    > via ge-0/0/0.0
201.100.0.1/32     *[Local/0] 00:38:10
                      Local via ge-0/0/0.0
224.0.0.5/32       *[OSPF/10] 00:31:58, metric 1
                      MultiRecv

> show ospf neighbor
Address          Interface              State     ID               Pri  Dead
198.18.100.2     ge-0/0/1.0             Full      172.16.20.2      128    35
172.16.25.2      ge-0/0/1.0             Full      172.16.20.2      128    39

vMX-2

interfaces {
    ge-0/0/0 {
        unit 0 {
            family inet {
                address 201.100.0.2/29;
            }
        }
    }
    ge-0/0/1 {
        unit 0 {
            family inet {
                address 172.16.25.2/30;
                address 198.18.100.2/29 {
                    vrrp-group 1 {
                        virtual-address 198.18.100.3;
                        priority 150;
                        accept-data;
                    }
                }
            }
        }
    }
    lo0 {
        unit 0 {
            family inet {
                address 172.16.20.2/32;
            }
        }
    }
}
protocols {
    bgp {
        local-as 100;
        group internal-peers {
            type internal;
            local-address 172.16.20.2;
            export ibgp-local-as;
            neighbor 172.16.20.1;
        }
    }
    ospf {
        area 0.0.0.0 {
            interface lo0.0 {
                passive;
            }
            interface ge-0/0/1.0;
        }
    }
}
policy-options {
    policy-statement ibgp-local-as {
        term t1 {
            then {
                next-hop self;
            }
        }
    }
}

vMX-2的路由表：

> show route

inet.0: 11 destinations, 11 routes (11 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.0/24         *[BGP/170] 00:03:36, MED 0, localpref 100, from 172.16.20.1
                      AS path: 200 I, validation-state: unverified
                    > to 172.16.25.1 via ge-0/0/1.0
                      to 198.18.100.1 via ge-0/0/1.0
172.16.20.1/32     *[OSPF/10] 00:33:17, metric 1
                      to 172.16.25.1 via ge-0/0/1.0
                    > to 198.18.100.1 via ge-0/0/1.0
172.16.20.2/32     *[Direct/0] 00:44:46
                    > via lo0.0
172.16.25.0/30     *[Direct/0] 00:34:22
                    > via ge-0/0/1.0
172.16.25.2/32     *[Local/0] 00:34:22
                      Local via ge-0/0/1.0
198.18.100.0/29    *[Direct/0] 00:41:49
                    > via ge-0/0/1.0
198.18.100.2/32    *[Local/0] 00:41:49
                      Local via ge-0/0/1.0
198.18.100.3/32    *[Local/0] 00:08:33
                      Local via ge-0/0/1.0
201.100.0.0/29     *[Direct/0] 00:49:58
                    > via ge-0/0/0.0
201.100.0.2/32     *[Local/0] 00:49:58
                      Local via ge-0/0/0.0
224.0.0.5/32       *[OSPF/10] 00:43:57, metric 1
                      MultiRecv

来自PC1的Ping：

PC1> ping 1.1.1.1
84 bytes from 1.1.1.1 icmp_seq=1 ttl=254 time=12.161 ms
84 bytes from 1.1.1.1 icmp_seq=2 ttl=254 time=12.250 ms
84 bytes from 1.1.1.1 icmp_seq=3 ttl=254 time=5.690 ms
84 bytes from 1.1.1.1 icmp_seq=4 ttl=254 time=9.649 ms
84 bytes from 1.1.1.1 icmp_seq=5 ttl=254 time=2.823 ms

追踪：

PC1> trace 1.1.1.1
trace to 1.1.1.1, 8 hops max, press Ctrl+C to stop
 1   172.16.25.2   2.584 ms  0.861 ms  0.645 ms
 2   172.16.25.1   2.450 ms  1.736 ms  1.723 ms
 3   *201.100.0.5   9.231 ms (ICMP type:3, code:3, Destination port unreachable)

我认为您的配置只是缺少iBGP的下一跳策略。

票数 4

Network Engineering用户

发布于 2018-11-03 13:24:56

什么是172.16.25.1？你在设置下一跳自我吗？默认情况下，IBGP广告中的前缀保留当前的下一跳(这将是传输)。

您可以修改Junos的BGP实现以保留所有路由，无论它们是否有效：https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/keep-edit-protocols-bgp.html

但我怀疑如果你不能跟踪这里还会发生更多的事情。你能提供你的拖拉机吗？您还可以包括traceroute的源地址吗？我看到了混合的私人地址，当追踪到互联网时，这些地址通常不会有帮助。

票数 0

页面原文内容由Network Engineering提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://networkengineering.stackexchange.com/questions/54339

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