Inter-As Topology - Juniper JUNOSE SOFTWARE FOR E SERIES 11.0.X - BGP AND MPLS CONFIGURATION GUIDE 2009-12-30 Configuration Manual

host1:pe1:pe11#ip8:pe1#trace mpls l3vpn 10.99.99.21/32 detail
Tracing VPN IPv4 prefix, timeout = 2 sec, Max TTL 32
MplsNextHopIndex 73 handle 8073322
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
Packet Flow Examples for Verifying MPLS Connectivity
Chapter 4: Monitoring MPLS
371