It's necessary to configure ISIS, forming adjacency, enable the carrying of Traffic Engineering extensions, enable RSVP and LSP signaling ( which in Cisco terminology are often called Traffic Engineering Tunnel ) and finally to enable the forwarding of MPLS Labeled packets.
Starting from my topology JNCIP delete on my Olive router "Zion" the two logical-system J4 and J6:
and proceed with the configuration of two new Cisco router:[edit] nick@zion# delete logical-systems J4 [edit] nick@zion# delete logical-systems J6
R4: IP address and IS-IS Routing
The IS-IS configuration is very simple, enable ISIS on the interfaces and set as a point-to-point link, (to avoid DIS election, speed-up and reduce the database).
In the IS-IS process specified the System ID ( "net" entry) define this as an only level-2 router and use the "wide style" mandatory metrics for the TE operation, and finally declare the loopback as passive to include in the topology.
but the adjacencies never come up, remaining in the INIT state:interface Loopback0 ip address 10.0.3.4 255.255.255.255 ! interface FastEthernet0/0 ip address 10.0.4.9 255.255.255.252 ip router isis isis network point-to-point ! interface FastEthernet0/1 ip address 10.0.2.6 255.255.255.252 ip router isis isis network point-to-point ! interface FastEthernet1/0 ip address 10.0.2.10 255.255.255.252 ip router isis isis network point-to-point ! router isis net 49.0000.0000.0004.00 is-type level-2-only metric-style wide passive-interface Loopback0 !
there is a MTU mistmatch, the Zion interface has and CLNS (ISO) MTU of 1493:R4#sh clns neighbors System Id Interface SNPA State Holdtime Type Protocol 0000.0000.0002 Fa0/0 0050.8be3.eb2c Init 24 L2 IS-IS 0000.0000.0003 Fa0/1 0050.8be3.eb2d Init 23 L2 IS-IS 0000.0000.0005 Fa1/0 0050.8be3.eb2c Init 20 L2 IS-IS
This is because Zion interfaces are using 802.1q and Olive uses a fixed MTU of 1500 bytes on FXP interfaces, reducing the effective packet length of 4 bytes, while Cisco routers are connected to in access-mode to the switch...nick@zion> show interfaces fxp2.204 Logical interface fxp2.204 (Index 82) (SNMP ifIndex 143) Description: ------- link ptp J2 <-> J4 -- Flags: SNMP-Traps VLAN-Tag [ 0x8100.204 ] Encapsulation: ENET2 Bandwidth: 0 Input packets : 6673 Output packets: 6931 Protocol inet, MTU: 1496 Flags: None Addresses, Flags: Is-Preferred Is-Primary Destination: 10.0.4.8/30, Local: 10.0.4.10, Broadcast: 10.0.4.11 Protocol iso, MTU: 1493 Flags: None Protocol mpls, MTU: 1484 Flags: None
The absence of adjacency depend on hello messages padding introduced for early detection of MTU problems.
The solution proposed is to reduce MTU just for the CLNS packet on the cisco side ( my hardware does not support changing interface MTU )
alternatively you can use the command "no hello padding" and all its variantsR4#conf t Enter configuration commands, one per line. End with CNTL/Z. R4(config)#int fast 0/0 R4(config-if)#clns mtu 1493 R4(config-if)#int fast 0/1 R4(config-if)#clns mtu 1493 R4(config-if)#int fast 1/0 R4(config-if)#clns mtu 1493 R4(config-if)#^Z
for example:
adjacency is now established and the database is populated ...R4(config)#router isis R4(config-router)#no hello padding point-to-point
R4#sh clns neighbors System Id Interface SNPA State Holdtime Type Protocol zion-J2 Fa0/0 0050.8be3.eb2c Up 25 L2 IS-IS zion-J3 Fa0/1 0050.8be3.eb2d Up 22 L2 IS-IS zion-J5 Fa1/0 0050.8be3.eb2c Up 20 L2 IS-IS
R4 : MPLS and IS-IS TE Database integrationR4#sh ip route isis | B ^Ga Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 22 subnets, 3 masks i L2 10.0.2.0/30 [115/20] via 10.0.2.9, FastEthernet1/0 [115/20] via 10.0.2.5, FastEthernet0/1 i L2 10.0.3.3/32 [115/10] via 10.0.2.5, FastEthernet0/1 ...
you must also enable the extensions required by RFC3784 necessary for TE information exchange, to control band allocation and label signaling via RSVP and finally the process of MPLS labeled packet:
globally enable LSP allocation
enable on all PE facing interface RSVP and MPLS packet processing like:mpls traffic-eng tunnels
estabilish the router-id ( TLV 134 ) and allow the necessary TE TLV exchange on all Level-2 adjacenciesinterface FastEthernet0/0 ip rsvp bandwidth mpls traffic-eng tunnels
router isis mpls traffic-eng router-id Loopback0 mpls traffic-eng level-2
this is the complete R4 configuration:
the R6 configuration is similar and available at the end of this post.! hostname R4 ! mpls traffic-eng tunnels ! interface Loopback0 ip address 10.0.3.4 255.255.255.255 ! interface FastEthernet0/0 ip address 10.0.4.9 255.255.255.252 ip router isis mpls traffic-eng tunnels clns mtu 1493 isis network point-to-point ip rsvp bandwidth ! interface FastEthernet0/1 ip address 10.0.2.6 255.255.255.252 ip router isis mpls traffic-eng tunnels clns mtu 1493 isis network point-to-point ip rsvp bandwidth ! interface FastEthernet1/0 ip address 10.0.2.10 255.255.255.252 ip router isis mpls traffic-eng tunnels clns mtu 1493 isis network point-to-point ip rsvp bandwidth ! router isis net 49.0000.0000.0004.00 is-type level-2-only metric-style wide passive-interface Loopback0 mpls traffic-eng router-id Loopback0 mpls traffic-eng level-2 !
LSP Setup
To verify the effective integration of the two platforms, let's configure two LSP (or TE Tunnels ), one from J2 to R6 and the simmetric from R6 to J2, reminding us that LSPs are always unidirectional.
We will not use any constraint, and hence the LSP will be allocated according to the best IGP metric the result should be:
LSP1 : J2 → R4 → R6 → J4
LSP2 : J5 → R4 → R6 → J2
The J2 configuration is simple:
This command requires an LSP to the address 10.0.9.6, resources allocation and Label signaling. If the entire process is successful, it immediately create an entry for the destination address in the inet.3 table, usually used to resolve the BGP next-hop, and that has precedence over the inet.0:protocols { mpls { label-switched-path J2-to-R6 { to 10.0.9.6; } }
the LSP is active:
the destination is installed in inet.3nick@zion> show mpls lsp ingress logical-system J2 Ingress LSP: 1 sessions To From State Rt P ActivePath LSPname 10.0.9.6 10.0.6.2 Up 0 * J2-to-R6 Total 1 displayed, Up 1, Down 0
The label allocated and signaled by R4 for this LSP is 16, the first label non-reservednick@zion> show route 10.0.9.6 logical-system J2 inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both 10.0.9.6/32 *[IS-IS/18] 00:51:24, metric 30 > to 10.0.4.1 via fxp2.203 to 10.0.4.9 via fxp2.204 inet.3: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both 10.0.9.6/32 *[RSVP/7] 00:49:32, metric 30 > to 10.0.4.9 via fxp2.204, label-switched-path J2-to-R6
The minimum configuration of R6 is:nick@zion> show route 10.0.9.6 logical-system J2 table inet.3 extensive | match Label Label-switched-path J2-to-R6 Label operation: Push 16
in IOS LSP is usually called “TE Tunnel” and configured as a tunnel interface: some notes about the configuration:interface Tunnel0 ip unnumbered Loopback0 tunnel destination 10.0.6.2 tunnel mode mpls traffic-eng tunnel mpls traffic-eng autoroute announce tunnel mpls traffic-eng path-option 10 dynamic !
in this type of tunnel there is no “tunnel source”
“autoroute announce” install in the routing table the destination through the tunnel
“path-option 10 dynamic” use just the IGP metric without costrain
show 2 tunnels “UP/UP”, one head and one tail.R6#sh mpls traffic-eng tunnels brief | b ^TU TUNNEL NAME DESTINATION UP IF DOWN IF STATE/PROT R6_t0 10.0.6.2 - Fa0/0 up/up J2-to-R6 10.0.9.6 Fa0/0 - up/up Displayed 1 (of 1) heads, 0 (of 0) midpoints, 1 (of 1) tails
IOS has just 1 table and this output can be disorienting (or the different Junos table :-) )
and the label used, allocated and signaled by J5 is in the tipical Junos range for this type of traffic:R6#sh ip route 10.0.6.2 Routing entry for 10.0.6.2/32 Known via "isis", distance 115, metric 30, type level-2 Redistributing via isis Last update from 10.0.6.2 on Tunnel0, 00:55:05 ago Routing Descriptor Blocks: * 10.0.6.2, from 10.0.6.2, via Tunnel0 Route metric is 30, traffic share count is 1
Also on the transit router can control the LSP allocatedR6#sh mpls traffic-eng tunnels tunnel 0 | i Label InLabel : - OutLabel : FastEthernet0/0, 299888
On Junos:
and on Cisco:nick@zion> show mpls lsp logical-system J5 Ingress LSP: 0 sessions Total 0 displayed, Up 0, Down 0 Egress LSP: 0 sessions Total 0 displayed, Up 0, Down 0 Transit LSP: 2 sessions To From State Rt Style Labelin Labelout LSPname 10.0.6.2 10.0.9.6 Up 1 1 SE 299888 17 R6_t0 10.0.9.6 10.0.6.2 Up 1 1 FF 299872 0 J2-to-R6 Total 2 displayed, Up 2, Down 0
In both cases the special label "implict-null" is used in place of PHP (Penultimate Hop Popping) because TE operations usually use the EXP Bit for traffic classification, which for some traffic reclassification may be different from the IP Precedence of the transported package ( and obviously also the traffic can not be IP... )R4#sh mpls traffic-eng tunnels brief | b ^TU TUNNEL NAME DESTINATION UP IF DOWN IF STATE/PROT J2-to-R6 10.0.9.6 Fa0/0 Fa1/0 up/up R6_t0 10.0.6.2 Fa1/0 Fa0/0 up/up Displayed 0 (of 0) heads, 2 (of 2) midpoints, 0 (of 0) tails R4#sh mpls traffic-eng tunnels | i Tunnel|Label LSP Tunnel J2-to-R6 is signalled, connection is up InLabel : FastEthernet0/0, 16 OutLabel : FastEthernet1/0, 299872 LSP Tunnel R6_t0 is signalled, connection is up InLabel : FastEthernet1/0, 17 OutLabel : FastEthernet0/0, implicit-null
One further note for the Cisco platform that can misleading:
analizing LFIB (Label Forwarding Information Base) used for MPLS packet forwarding on R4 shows "Pop Label"
R4#sh mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or VC or Tunnel Id Switched interface 16 299872 10.0.6.2 12053 [1] \ 0 Fa1/0 10.0.2.9 17 Pop Label 10.0.9.6 0 [248] 0 Fa0/0 10.0.4.10
but this mean ( from Cisco documentation ) :
No Label - Means that there is no label for the destination from the next hop or that label switching is not enabled on the outgoing interface.
** Pop Label ** - Means that the next hop advertised an implicit NULL label for the destination and that the router popped the top label.
Aggregate - Means there are several prefixes for one local label. This entry is used when IPv6 is configured on edge routers to transport IPv6 traffic over an IPv4 MPLS network.
Nothing particularly exciting at this point, only a couple of suggestions like the hello padding ISIS and verification of proper implementation of the two LSPs, it is now time to think about what to do with this two LSPs...
final Zion Configuration here
final R4 Configuration here
final R6 Configuration here
Good post!!
RispondiElimina