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ArubaOS-CX BGP default route

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  • 1.  ArubaOS-CX BGP default route

    Posted 28 days ago
    Hello,

    We're currently using two 6300M switches to connect to two 10G CPE's from a internet provider. both with theire own /30 subnet and both within the same public AS. On customer side we use a single private AS.

    On the first link we receive a 0.0.0.0 route with a metric of 0, on the second link we get a route 0.0.0.0 with a metric of 1000.

    Somehow the second switch doesn't seem to like it. The 0.0.0.0 apears and disapears.

    ***************************************
    Iteration : 90 Command : show ip route
    ***************************************
    
    Displaying ipv4 routes selected for forwarding
    
    Origin Codes: C - connected, S - static, L - local
    R - RIP, B - BGP, O - OSPF
    Type Codes: E - External BGP, I - Internal BGP, V - VPN, EV - EVPN
    IA - OSPF internal area, E1 - OSPF external type 1
    E2 - OSPF external type 2
    
    VRF: default
    
    Prefix Nexthop Interface VRF(egress) Origin/ Distance/ Age
    Type Metric
    ---------------------------------------------------------------------------------------------------------
    0.0.0.0/0 1xx.1yy.200.185 1/1/27 - B/E [20/1000] 00h:10m:51s
    1xx.1yy.198.96/27 - vlan144 - C [0/0] -
    1xx.1yy.198.99/32 - vlan144 - L [0/0] -
    1xx.1yy.200.184/30 - 1/1/27 - C [0/0] -
    1xx.1yy.200.186/32 - 1/1/27 - L [0/0] -
    
    Total Route Count : 5
    
    
    
    ***************************************
    Iteration : 91 Command : show ip route
    ***************************************
    
    Displaying ipv4 routes selected for forwarding
    
    Origin Codes: C - connected, S - static, L - local
    R - RIP, B - BGP, O - OSPF
    Type Codes: E - External BGP, I - Internal BGP, V - VPN, EV - EVPN
    IA - OSPF internal area, E1 - OSPF external type 1
    E2 - OSPF external type 2
    
    VRF: default
    
    Prefix Nexthop Interface VRF(egress) Origin/ Distance/ Age
    Type Metric
    ---------------------------------------------------------------------------------------------------------
    1xx.1yy.198.96/27 - vlan144 - C [0/0] -
    1xx.1yy.198.99/32 - vlan144 - L [0/0] -
    1xx.1yy.200.184/30 - 1/1/27 - C [0/0] -
    1xx.1yy.200.186/32 - 1/1/27 - L [0/0] -
    
    Total Route Count : 4
    
    
    
    ***************************************
    Iteration : 92 Command : show ip route
    ***************************************
    
    Displaying ipv4 routes selected for forwarding
    
    Origin Codes: C - connected, S - static, L - local
    R - RIP, B - BGP, O - OSPF
    Type Codes: E - External BGP, I - Internal BGP, V - VPN, EV - EVPN
    IA - OSPF internal area, E1 - OSPF external type 1
    E2 - OSPF external type 2
    
    VRF: default
    
    Prefix Nexthop Interface VRF(egress) Origin/ Distance/ Age
    Type Metric
    ---------------------------------------------------------------------------------------------------------
    0.0.0.0/0 1xx.1yy.200.185 1/1/27 - B/E [20/1000] 00h:10m:55s
    1xx.1yy.198.96/27 - vlan144 - C [0/0] -
    1xx.1yy.198.99/32 - vlan144 - L [0/0] -
    1xx.1yy.200.184/30 - 1/1/27 - C [0/0] -
    1xx.1yy.200.186/32 - 1/1/27 - L [0/0] -
    
    Total Route Count : 5​

    Did anyone experience this one before? When I test in my lab with virtual cx switches its seems to start when I add a metric to the second connection.


    With kind regards,

    Rens

    ------------------------------
    Rens Kluitmans
    ------------------------------


  • 2.  RE: ArubaOS-CX BGP default route

    Posted 27 days ago
    only the preferred routes gets added in the routing table.
    But you can see the bgp learnt routes with "show ip route bgp" and that should show both the default routes that were learnt with their respective metric
    if those routes are appearing/disappearing then it could possibly point to a unstable BGP neighbour state.
    you can check the bgp neighbour state with "show bgp summary"

    ------------------------------
    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba.
    ------------------------------



  • 3.  RE: ArubaOS-CX BGP default route

    Posted 27 days ago
    Hello Ariya,

    It seems the BGP connections are stable. The 0.0.0.0 was in there for more than 10 minutes.

    show bgp all output seems correct to me.

    RT0002(config)# show bgp all
    Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
                  i internal, e external S Stale, R Removed, a additional-paths
    Origin codes: i - IGP, e - EGP, ? - incomplete
    
    VRF : default
    Local Router-ID 1xx.1yy.200.186
    
    Address-family : IPv4 Unicast
    -----------------------------
        Network            Nexthop         Metric     LocPrf     Weight Path
    *>i 0.0.0.0/0          1xx.1yy.200.181 0          100        0       39686 i
    * e 0.0.0.0/0          1xx.1yy.200.185 1000       100        0       39686 i
    *>  1xx.1yy.198.96/27  0.0.0.0         0          100        0       i
    * i 1xx.1yy.198.96/27  1xx.1yy.198.98  0          100        0       i
    *>  1xx.1yy.200.184/30 0.0.0.0         0          100        0       i
    Total number of entries 5
    
    Address-family : IPv6 Unicast
    -----------------------------
        Network            Nexthop         Metric     LocPrf     Weight Path
    Total number of entries 0
    
    Address-family : L2VPN EVPN
    -----------------------------
         Network                                               Nexthop         Metric     LocPrf    Weight   Path
    ------------------------------------------------------------------------------------------------------------
    Total number of entries 0
    ​

    Regards,

    Rens



    ------------------------------
    Rens
    ------------------------------



  • 4.  RE: ArubaOS-CX BGP default route

    Posted 27 days ago
    The above output is without the next-hop-self command om the RT0001 and RT0002.
    With the command in place the ip address 1xx.1yy.200.181 is replaced with the iBGP neigbour address

    ------------------------------
    Rens
    ------------------------------



  • 5.  RE: ArubaOS-CX BGP default route

    Posted 27 days ago
    It is highly recommend to use next-hop-self for the peering between your 2x 6300, so that the IP address of your internet ISP routers does not need to be known in the IGP. Route-flapping like you experience is typically due to recursive lookup of next-hop failing due to eBGP next-hop not in routing table.

    ------------------------------
    Vincent Giles
    ------------------------------



  • 6.  RE: ArubaOS-CX BGP default route

    Posted 27 days ago
    spot on Vincent.

    ------------------------------
    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba.
    ------------------------------