Increase TTL of IPv6 packets

Installing and Using OpenWrt Network and Wireless Configuration
1

I want to forward broadcast ip packtes between subnets. For this, the TTL of the broadcast packages needs to be increased. For IPv4, this can be done with firewall rules like iptables -t mangle -A PREROUTING -d 239.255.255.250 -j TTL --ttl-inc 1 alfter installing the package iptables-mod-ipopt. For ip6tables, there is no package ip6tables-mod-ipopt. The command ip6tables -t mangle -A PREROUTING -d 239.255.255.250 -j TTL --ttl-inc 1 fails with the message:

ip6tables v1.8.3 (legacy): unknown option "--ttl-inc"

How can I increase the TTL of IPv6 packets?

2

Ipv6 doesn't have ttl, it has hop limit. Try the hl module.

3

Great, thanks! :slight_smile: The following ip6tables command is the equivalent for the above mentioned iptables command (I use it do enable forwarding of SSDP multicasts with smcroute):

ip6tables -t mangle -A PREROUTING -d ff02::c -j HL --hl-inc 1
4

Any idea why the name is changed? According to Wikipedia there is no technical difference.

5

In theory, under IPv4, time to live is measured in seconds, although every host that passes the datagram must reduce the TTL by at least one unit. In practice, the TTL field is reduced by one on every hop. To reflect this practice, the field is renamed hop limit in IPv6.