[j-nsp] Multipath BGP issue

[Paul Stewart]

Hey folks.

 

I'd like to know if I'm being dumb or if my problem is legit ;)  MX480
platform running 10.0R3.10.

 

Customer has BGP connection from us - been in service for long time and
works fine.  Customer now added a second BGP connection to us and we've run
into a problem.  Traffic from us to the customer (inbound Internet from
customer perspective) will only prefer one path.

 

So obvious answer I thought was multipath in the configuration (which has
always been present) however see the config and output below..

 

First configuration (customer AS changed to 12345 to protect the innocent):

 

{master}[edit protocols bgp group transit-customers-v4]

paul at core1.toronto1# show

type external;

description IP_Transit_Customers_Full_V4;

advertise-inactive;

export [ ospf_bgp outbound-transit-v4 ];

multipath;

neighbor xx.xxx.x.98 {

    description xxxxxxxxxxxxxxx;

    import inbound-iaw;

    peer-as 12345;

}

neighbor xx.xxx.x.74 {

    description xxxxxxxxxxxxxxxxxxxx;

    import inbound-iaw;

    peer-as 12345;

}

 

{master}[edit policy-options policy-statement inbound-iaw]

paul at core1.toronto1# show

term iaw1 {

    from {

        prefix-list ASxxxxx;

    }

    then {

        local-preference 300;

        community add customer_nets;

        accept;

    }

}

term iaw2 {

    then reject;

}

 

 

The same policy is applied on both sessions - original session works fine
and the second session shows the same route being accepted (both BGP
sessions have an active route accepted)

 

paul at core1.toronto1> show route receive-protocol bgp xx.xxx.7.98

 

inet.0: 362929 destinations, 835229 routes (362908 active, 21 holddown, 18
hidden)

  Prefix                  Nexthop              MED     Lclpref    AS path

* xx.49.32.0/19           xx.124.7.98          0                  12345 I

 

paul at core1.toronto1> show route receive-protocol bgp xx.xxx.46.74

 

inet.0: 362933 destinations, 835221 routes (362906 active, 27 holddown, 18
hidden)

  Prefix                  Nexthop              MED     Lclpref    AS path

  xx.49.32.0/19           xx.124.46.74         0                  12345 I

 

 

So this is where things start to fall apart - had a JTAC ticket open on this
since yesterday morning and they are still "digesting" my configuration and
various captures.  You can see that only one path is being preferred but
why?

 

 

paul at core1.toronto1> show route xx.49.32.0/19

 

inet.0: 362924 destinations, 835210 routes (362912 active, 12 holddown, 18
hidden)

+ = Active Route, - = Last Active, * = Both

 

xx.49.32.0/19      *[BGP/170] 1d 10:18:43, MED 0, localpref 300

                      AS path: 12345 I

                      to xx.124.46.74 via xe-4/3/0.68

                    > to xx.124.7.98 via xe-4/3/0.67

                    [BGP/170] 1d 10:18:43, MED 0, localpref 300

                      AS path: 12345 I

                    > to xx.124.46.74 via xe-4/3/0.68

                    [BGP/170] 17:39:04, MED 100, localpref 200, from
xxx.32.245.78

                      AS path: xxxxx 12345 I

                    > to xxx.32.245.56 via xe-4/3/0.56

 

paul at core1.toronto1> show route forwarding-table destination xx.49.32.0/19

Routing table: default.inet

Internet:

Destination        Type RtRef Next hop           Type Index NhRef Netif

xx.49.32.0/19      user     0

                   user     0 xx.124.7.98        ucst  1681     4
xe-4/3/0.67

 

paul at core1.toronto1> show route xx.49.32.0/19 detail

 

inet.0: 362928 destinations, 835260 routes (362898 active, 30 holddown, 18
hidden)

xx.49.32.0/19 (3 entries, 1 announced)

        *BGP    Preference: 170/-301

                Next hop type: Router

                Next-hop reference count: 2

                Source: xx.124.7.98

                Next hop: xx.124.46.74 via xe-4/3/0.68

                Next hop: xx.124.7.98 via xe-4/3/0.67, selected

                State: <Active Ext>

                Local AS: 11666 Peer AS: 12345

                Age: 1d 10:34:01        Metric: 0

                Task: BGP_12345.xx.124.7.98+179

                Announcement bits (4): 0-KRT 5-BGP RT Background 6-Resolve
tree 1 9-RT

                AS path: 12345 I (Atomic) Aggregator: 12345 xx.49.32.226

                AS path:

                AS path: Recorded

                Communities: 11666:4000

                Accepted Multipath

                Localpref: 300

                Router ID: xx.49.32.226

         BGP    Preference: 170/-301

                Next hop type: Router

                Next-hop reference count: 1

                Source: xx.124.46.74

                Next hop: xx.124.46.74 via xe-4/3/0.68, selected

                State: <NotBest Ext>

                Inactive reason: Not Best in its group - Update source

                Local AS: 11666 Peer AS: 12345

                Age: 1d 10:34:01        Metric: 0

                Task: BGP_12345.xx.124.46.74+179

                AS path: 12345 I (Atomic) Aggregator: 12345 xx.49.32.226

                AS path:

                AS path: Recorded

                Communities: 11666:4000

                Accepted

                Localpref: 300

                Router ID: xx.49.32.226

 

Is there a legit issue here somewhere?  JTAC seemed to indicate they wanted
to further investigate my import policy but I don't see anything wrong
here.. ?

 

Thanks for any input - this list is typically MUCH faster than JTAC for
answers and I have a very anxious customer on my hands ;)

 

Paul