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ArubaOS-CX BGP default route

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  • 1.  ArubaOS-CX BGP default route

    Posted Dec 20, 2021 10:09 AM
    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

    EMPLOYEE
    Posted Dec 20, 2021 06:32 PM
    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.
    ------------------------------

    Original Message


  • 3.  RE: ArubaOS-CX BGP default route

    Posted Dec 21, 2021 02:16 AM
    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
    ------------------------------

    Original Message


  • 4.  RE: ArubaOS-CX BGP default route

    Posted Dec 21, 2021 02:21 AM
    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
    ------------------------------

    Original Message


  • 5.  RE: ArubaOS-CX BGP default route

    EMPLOYEE
    Posted Dec 21, 2021 06:39 AM
    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
    ------------------------------

    Original Message


  • 6.  RE: ArubaOS-CX BGP default route

    EMPLOYEE
    Posted Dec 21, 2021 06:57 AM
    spot on Vincent.

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

    Original Message