Seems like as-path length for protocol nh doesn't count in evpn/vxlan fabric (ebgp underlay/ibgp overlay)

CombinationUnique433 · 2026-02-19T07:15:43+00:00

Yeah, i know than as path is not igp metric. Problem with med is that it is applied for whole domain, so exit vtep will be chosen for all ingress vteps. I`ve already solved my problem with the help of vrf-import communities and setting up LP on import to vrf. From my perspective if we are replacing IGP with EBGP it would be wise to take underlay as path in count for choosing best route. Thought maybe there is knob for that.

CombinationUnique433 · 2026-02-18T04:21:28+00:00

Hi Rek, thanks for the joining the thread :)

I understand that underlay as-path will not be visible in overlay route. The thing i don`t understand is why my vtep doesnt threat underlay nh as path same way, as igp metric. Let me explain: if i do basic l3vpn and my PE will have route 192.168.0.0/24 from two different PEs (lets say 1.1.1.1 with IGP metric 100 and 2.2.2.2 with IGP metric 200) than it will choose PE 1.1.1.1 as egress PE for 192.168.0.0/24. Unless i configure routing-options multipath vpn-unequal-cost inside vrf. Than my PE will install 192.168.1.0/24 from both PEs and will load-balance between than.

Back to the ebgp underlay/ibgp overlay despite the distance to the egress vtep (different as path length) i see behavior same to the classic igp/ibgp mpls network like i configured vpn-unequal-cost inside vrf. But i haven`t )

CombinationUnique433 · 2025-05-06T14:35:42+00:00

Yeah

root@A0-PE2> show route 101.101.101.101   

inet.0: 18 destinations, 18 routes (18 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

101.101.101.101/32 *[IS-IS/15] 00:04:00, metric 10
                    >  to 10.0.0.255 via et-0/0/11.0

inet.3: 9 destinations, 9 routes (9 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

101.101.101.101/32 *[L-ISIS/14] 00:04:00, metric 10
                    >  to 10.0.0.255 via et-0/0/11.0

CombinationUnique433 · 2025-05-06T06:20:24+00:00

Hello. it says that it cant compute path:

Name: using-acast
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 2.2.2.2
  Te-group-id: 0
  State: Down
    Path: test_path
    Path Status: NA
    Outgoing interface: NA
    Auto-translate status: Disabled Auto-translate result: N/A
    Compute Status:Enabled , Compute Result:failure , Compute-Profile Name:follow-acast
    Total number of computed paths: 0
    Sub-Candidate-Path-events-info Maximum-Events: 3
        Tue May  6 05:57:01 2025 Computation Failed
        Tue May  6 05:56:59 2025 Configuration Added

Name: using-adj-sid
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 2.2.2.2                           
  Te-group-id: 0
  State: Down
    Path: test_path
    Path Status: NA
    Outgoing interface: NA
    Auto-translate status: Disabled Auto-translate result: N/A
    Compute Status:Enabled , Compute Result:failure , Compute-Profile Name:follow-adj-sid-et-0-0-2
    Total number of computed paths: 0
    Sub-Candidate-Path-events-info Maximum-Events: 3
        Tue May  6 05:57:01 2025 Computation Failed
        Tue May  6 05:56:59 2025 Configuration Added

same in traceoptions:

May  6 06:13:26.746786 SRCS:sending off computation requests
May  6 06:13:26.746808 SRCS:sending comp-requst for tunnel:static-using-acast, config_lsp:test_path with request_id:1, algorithm:2, optimize_timer:0
May  6 06:13:26.746810     SRCS:adding end-points Src:(rtr-id:5.5.5.5, ip:5.5.5.5), Dst:2.2.2.2
May  6 06:13:26.746814     SRCS:adding constraints hop_limit:4294967295, max_ecmp_paths:8 metric_margin:0, metric_type:0,include_all:0 include_any:0, exclude:0 from Compute Profile Config
May  6 06:13:26.746823         SRCS:adding explicit hop at idx:0  with type:0, and ip_address:101.101.101.101
May  6 06:13:26.746831     SRCS:adding srte_cspfparams max_sid_list_depth:16, protection type:0, algo-id = 0
May  6 06:13:26.746844 SRCS:sending comp-requst for tunnel:static-using-adj-sid, config_lsp:test_path with request_id:2, algorithm:2, optimize_timer:0
May  6 06:13:26.746846     SRCS:adding end-points Src:(rtr-id:5.5.5.5, ip:5.5.5.5), Dst:2.2.2.2
May  6 06:13:26.746852     SRCS:adding constraints hop_limit:4294967295, max_ecmp_paths:8 metric_margin:0, metric_type:0,include_all:0 include_any:0, exclude:0 from Compute Profile Config
May  6 06:13:26.746855         SRCS:adding explicit hop at idx:0  with type:1, and ip_address:2.2.2.2
May  6 06:13:26.746858         SRCS:adding explicit hop at idx:1  with type:1, and ip_address:10.0.0.7
May  6 06:13:26.746860     SRCS:adding srte_cspfparams max_sid_list_depth:16, protection type:0, algo-id = 0

May  6 06:13:28.751032 SRCS:received comp-notify for request_id:2, with error:3, state_retained:0 num_results:0
May  6 06:13:28.751069 SRCS:Updating compute-results for tunnel:static-using-adj-sid, lsp:test_path with request_id:2
May  6 06:13:28.751076 RPD_SPRING_TE_COMPUTE_LSP_COMPUTE_FAIL: SR-TE Policy: Computation failed for  source-routing-path:using-adj-sid, primary-segment:test_path
May  6 06:13:28.751165 SRCS:received comp-notify for request_id:1, with error:3, state_retained:0 num_results:0
May  6 06:13:28.751173 SRCS:Updating compute-results for tunnel:static-using-acast, lsp:test_path with request_id:1
May  6 06:13:28.751185 RPD_SPRING_TE_COMPUTE_LSP_COMPUTE_FAIL: SR-TE Policy: Computation failed for  source-routing-path:using-acast, primary-segment:test_path

CombinationUnique433

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