dhcpcd-discuss

Hi Daniel

On 22/12/2019 07:11, Daniel Corbe wrote:
> I've got a bit of a situation I'm stuck on and I'd appreciate any
> guidance anyone has to offer on this.
>
> I have a Comcast cable modem.  eth1 is my connection to the cable
> modem and eth2 is my LAN.
>
> When I let dhcpcd do its thing without specifying any
> interface-specific configuration, I get an auto-configured address on
> my outside interface:
>
> router:~# ifconfig eth1
> eth1      Link encap:Ethernet  HWaddr 18:E8:29:4C:4C:52
>            inet addr:73.57.99.182  Bcast:255.255.255.255  Mask:255.255.254.0
>            inet6 addr: 2001:558:6030:7c:38e8:d8d8:7e9e:730a/128 Scope:Global
>            inet6 addr: fe80::1ae8:29ff:fe4c:4c52/64 Scope:Link
>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>            RX packets:2385 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:2539 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:1000
>            RX bytes:894141 (873.1 KiB)  TX bytes:650792 (635.5 KiB)
>
> However, the moment I add any interface-specific configuration, the
> autoconfigure address on the outside interface goes away.  However, I
> do actually get my prefix and it gets put on the correct interface:
>
> router:~# ifconfig eth1
> eth1      Link encap:Ethernet  HWaddr 18:E8:29:4C:4C:52
>            inet addr:73.57.99.182  Bcast:255.255.255.255  Mask:255.255.254.0
>            inet6 addr: fe80::1ae8:29ff:fe4c:4c52/64 Scope:Link
>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>            RX packets:19299 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:17034 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:1000
>            RX bytes:7641535 (7.2 MiB)  TX bytes:4799347 (4.5 MiB)
>
> router:~# ifconfig eth2
> eth2      Link encap:Ethernet  HWaddr 18:E8:29:4C:4C:53
>            inet addr:10.0.0.1  Bcast:0.0.0.0  Mask:255.255.255.0
>            inet6 addr: 2601:588:c000:3a9::1/64 Scope:Global
>            inet6 addr: fe80::1ae8:29ff:fe4c:4c53/64 Scope:Link
>            inet6 addr: fe80::b35f:254c:58af:66e1/64 Scope:Link
>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>            RX packets:18210 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:18612 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:1000
>            RX bytes:5040165 (4.8 MiB)  TX bytes:7602467 (7.2 MiB)
>
> This unfortunately causes IPv6 to stop working completely:
>
> router:~# ping6 www.google.com
> PING www.google.com (2607:f8b0:4008:803::2004): 56 data bytes
> ping6: sendto: Network unreachable
>
> I'm pretty sure the problem is Comcast doesn't use link-local
> addresses for routing and are expecting me to continue to carry the
> autoconfigured address.
>
> Here's my running config:
>
> router:~# cat /etc/dhcpcd.conf
> # A sample configuration for dhcpcd.
> # See dhcpcd.conf(5) for details.
>
> # Allow users of this group to interact with dhcpcd via the control socket.
> #controlgroup wheel
>
> # Inform the DHCP server of our hostname for DDNS.
> hostname
>
> # Use the hardware address of the interface for the Client ID.
> #clientid
> # or
> # Use the same DUID + IAID as set in DHCPv6 for DHCPv4 ClientID as per RFC4361.
> # Some non-RFC compliant DHCP servers do not reply with this set.
> # In this case, comment out duid and enable clientid above.
> duid
>
> # Persist interface configuration when dhcpcd exits.
> persistent
>
> # Rapid commit support.
> # Safe to enable by default because it requires the equivalent option set
> # on the server to actually work.
> option rapid_commit
>
> # A list of options to request from the DHCP server.
> option domain_name_servers, domain_name, domain_search, host_name
> option classless_static_routes
> # Respect the network MTU. This is applied to DHCP routes.
> option interface_mtu
>
> # Most distributions have NTP support.
> #option ntp_servers
>
> # A ServerID is required by RFC2131.
> require dhcp_server_identifier
>
> # Generate SLAAC address using the Hardware Address of the interface
> #slaac hwaddr
> # OR generate Stable Private IPv6 Addresses based from the DUID
> slaac private
>
> # IPv6 Only
> #ipv6only
>
> # Wait for IP before forking to background
> waitip 6
>
> # Use the interface connected to WAN
> interface eth1
>      ipv6rs # enable routing solicitation get the default IPv6 route
>      ipv6ra_autoconf
>      iaid 1
>      ia_pd 1/::/62 eth2/0/64

The issue is with your configuartion :)
Because you have specificall requested a DHCP6 address, it overrides any default 
as suggested by dhcpcd or the IPv6 router.

Try this:

interface eth1
     ipv6rs # enable routing solicitation get the default IPv6 route
     ipv6ra_autoconf
     ia_pd 1/::/62 eth2/0/64
     ia_na 1

Note that the first two entries are on by default and you haven't disabled them 
in the config so you could remove them.

Roy