Configuration

To disable the decrement of the TTL value of inner payload header of an IP-in-IP packet, use the following steps:

1. Enter the global configuration mode.

2. Disable the decrement of TTL value of inner payload header of an IP-in-IP packet.

Configuration Example

/* Enter the Global Configuration mode. */
Router# configure

/* Disable the decrement of TTL value of inner payload header of an IP-in-IP packet. */
Router(config)# hw-module profile cef ttl tunnel-ip decrement disable
Router(config)# commit

Associated Commands

• hw-module profile cef ttl tunnel-ip decrement disable

Stacked IP Header in an Encapsulated Packet

The encapsulated packet has an outer IPv4 header that is stacked over the original IPv4 header, as shown in the following illustration.

Configuration

You can use the following sample configuration in the routers to decapsulate the packet as it traverses the IP-in-IP tunnel:

Router(config)# interface loopback 0
Router(config-if)# ipv4 address 127.0.0.1/32
Router(config-if)# no shutdown
Router(config-if)# interface tunnel-ip 10
Router(config-if)# ipv4 unnumbered loopback 1
Router(config-if)# tunnel mode ipv4 decap 
Router(config-if)# tunnel source loopback 0

• tunnel-ip: configures an IP-in-IP tunnel interface.

• ipv4 unnumbered loopback address: enables ipv4 packet processing without an explicit address, except for loopback address.

• tunnel mode ipv4 decap: enables IP-in-IP decapsulation.

• tunnel source: indicates the source address for the IP-in-IP decap tunnel with respect to the router interface.

Note	You can configure the tunnel destination only if you want to decapsulate packets from a particular destination. If no tunnel destination is configured, then all the ip-in-ip ingress packets on the configured interface are decapsulated.

Running Configuration

Router# show running-config interface tunnel-ip 10
...
interface tunnel-ip 10
ipv4 unnumbered loopback 1
tunnel mode ipv4 decap

Extended ACL to Match the Outer Header for IP-in-IP Decapsulation

Starting with Cisco IOS XR Software Release 7.0.14, extended ACL has to match on the outer header for IP-in-IP Decapsulation. Extended ACL support reduces mirrored traffic throughput. This match is based only on the IPv4 protocol, and extended ACL is applied to the received outermost IP header, even if the outer header is locally terminated.

ECMP Hashing Support for Load Balancing

The system inherently supports the n-tuple hash algorithm. The first inner header in the n-tuple hashing includes the source port and the destination port of UDP / TCP protocol headers.

The load balancing performs these functions:

• Incoming data traffic is distributed over multiple equal-cost connections.

• Incoming data traffic is distributed over multiple equal-cost connections member links within a bundle interface.

• Layer 2 bundle and Layer 3 (network layer) load-balancing decisions are taken on IPv4, and IPv6. If it is an IPv4 or an IPv6 payload, then an n-tuple hashing is done.

• An n-tuple hash algorithm provides more granular load balancing and used for load balancing over multiple equal-cost Layer 3 (network layer) paths. The Layer 3 (network layer) path is on a physical interface or on a bundle interface.

• The n-tuple load-balance hash calculation contains:

  • Source IP address

  • Destination IP address

  • IP Protocol type

  • Router ID

  • Source port

  • Destination port

  • Input interface