README.md: add caveats section
Robert Edmonds
10 years ago
| 49 | 49 | multi_table 2 |
| 50 | 50 | multi_gateway 203.0.113.1 |
| 51 | 51 | ``` |
| 52 | ||
| 53 | Caveats | |
| 54 | ------- | |
| 55 | ||
| 56 | + Do not specify a prefix in `multi_gateway_prefixes` that overlaps one of the | |
| 57 | subnets directly attached to the host. | |
| 58 | ||
| 59 | + IPv6 is supported, but it is implemented in a slightly different way than | |
| 60 | IPv4. The `multi_gateway_weight` option is not supported for IPv6 gateways. | |
| 61 | The first IPv6 gateway configured is used instead, unless a specific prefix is | |
| 62 | configured to use a particular gateway using the `multi_gateway_prefixes` | |
| 63 | option. | |
| 64 | ||
| 65 | + `ifup` disables stateless address autoconfiguration when the `static` method | |
| 66 | is used with the `inet6` address family, however it does *not* disable the | |
| 67 | learning of routes from IPv6 router advertisements. It is recommended to place | |
| 68 | an executable script in the `/etc/network/if-pre-up.d` directory containing | |
| 69 | something like the following contents: | |
| 70 | ||
| 71 | ``` | |
| 72 | #!/bin/sh | |
| 73 | if test "$IFACE" = "--all"; then | |
| 74 | exit 0 | |
| 75 | fi | |
| 76 | if test "$METHOD" != "static"; then | |
| 77 | exit 0 | |
| 78 | fi | |
| 79 | IFACE="$(echo $IFACE | cut -f1 -d:)" | |
| 80 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/autoconf | |
| 81 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_dad | |
| 82 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_ra | |
| 83 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_ra_defrtr | |
| 84 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_ra_pinfo | |
| 85 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_ra_rtr_pref | |
| 86 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_redirects | |
| 87 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_source_route | |
| 88 | echo 0 > /proc/sys/net/ipv6/conf/$IFACE/dad_transmits | |
| 89 | ``` |