Inter-As Topology - Juniper JUNOSE 11.2.X BGP AND MPLS Configuration Manual

JunosE 11.2.x BGP and MPLS Configuration Guide
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1 0ms 10.33.33.33 Label switched at stack-depth/2
TLV Interface and Label stack 20 bytes
Router 10.33.33.33 Intf 10.10.10.2
[L34 EXP 0 TTL 1] [L68 EXP 0 S TTL 1]
TLV Downstream mapping 24 bytes
Router 10.31.31.2 Intf 10.31.31.1 mtu 9180
[L56 EXP 0 LDP] [L68 EXP 0 S Unknown]
TLV Downstream mapping 24 bytes
Router 10.34.34.2 Intf 10.34.34.1 mtu 1500
[L79 EXP 0 LDP] [L68 EXP 0 S Unknown]
2 2ms 10.55.55.55 Label switched at stack-depth/2
TLV Interface and Label stack 20 bytes
Router 10.55.55.55 Intf 10.34.34.2
[L79 EXP 0 TTL 1] [L68 EXP 0 S TTL 2]
TLV Downstream mapping 24 bytes
Router 10.120.120.2 Intf 10.120.120.1 mtu 1500
[L43 EXP 0 LDP] [L68 EXP 0 S Unknown]
3 3ms 10.2.2.2 Replying router is an egress for the FEC at stack depth
TLV Pad 20 bytes
TLV Interface and Label stack 20 bytes
Router 10.2.2.2 Intf 10.120.120.2
[L43 EXP 0 TTL 1] [L68 EXP 0 S TTL 3]
host1:pe1#trace mpls l3vpn vrf pe11 10.99.98.21/32 reply pad-tlv exp-bits 5
detail
Tracing VPN IPv4 prefix, timeout = 2 sec, Max TTL 32
Handle 1921136 MplsNextHopIndex 78 [L68,L34]
1 0ms 10.33.33.33 Label switched at stack-depth/2
TLV Pad 20 bytes
TLV Interface and Label stack 20 bytes
Router 10.33.33.33 Intf 10.10.10.2
[L34 EXP 5 TTL 1] [L68 EXP 0 S TTL 1]
TLV Downstream mapping 24 bytes
Router 10.31.31.2 Intf 10.31.31.1 mtu 9180
[L56 EXP 5 LDP] [L68 EXP 0 S Unknown]
TLV Downstream mapping 24 bytes
Router 10.34.34.2 Intf 10.34.34.1 mtu 1500
[L79 EXP 5 LDP] [L68 EXP 0 S Unknown]
2 2ms 10.55.55.55 Label switched at stack-depth/2
TLV Pad 20 bytes
TLV Interface and Label stack 20 bytes
Router 10.55.55.55 Intf 10.34.34.2
[L79 EXP 5 TTL 1] [L68 EXP 0 S TTL 2]
TLV Downstream mapping 24 bytes
Router 10.120.120.2 Intf 10.120.120.1 mtu 1500
[L43 EXP 5 LDP] [L68 EXP 0 S Unknown]
3 3ms 10.2.2.2 Replying router is an egress for the FEC at stack depth
TLV Pad 20 bytes
TLV Interface and Label stack 20 bytes
Router 10.2.2.2 Intf 10.120.120.2
[L43 EXP 5 TTL 1] [L68 EXP 0 S TTL 3]

Inter-AS Topology

When an L3VPN ping or trace is transmitted, the TTL value on the inner (VPN) label is
set to 1 by default. This value causes the TTL to expire on the egress PE of the L3VPN
LSP and an echo reply can be sent back to the source. However, in an inter-AS topology,
this behavior might result in premature termination of the ping or trace. You can use the
bottom-label-ttl keyword to avoid this problem.
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