Hot answers tagged

14

Stateful autoconfiguration of IPv6 is the equivalent to the use of DHCP in IPv4. It requires a DHCPv6 service to provide the IPv6 address to the client device and that both client device and server maintain the "state" of that address (i.e. lease time, etc). Stateless autoconfiguration of IPv6 allows the client device to self-configure its IPv6 address and ...


13

A host performs Duplicate Address Detection (DAD) before actually activating the given address on the interface RFC 2462 has to say about this: 5.4. Duplicate Address Detection Duplicate Address Detection is performed on unicast addresses prior to assigning them to an interface whose DupAddrDetectTransmits variable is greater than zero. ...


11

IPv6 has more options for configuring addresses than IPv4. The process works as follows: A new client joins the network and sends a Router Solicitation (RS) Each router (can be multiple) sends a Router Advertisement (RA) This happens both on request (when receiving an RS) as well as periodically The RA contains a lot of information on how the network is ...


9

In RFC 7084, it also states: W-1: When the router is attached to the WAN interface link, it MUST act as an IPv6 host for the purposes of stateless [RFC4862] or stateful [RFC3315] interface address assignment. So in short, yes - a router should be able to autoconfigure an IPv6 address for its WAN interface. In reality though, most ...


8

Prefix delegation is a DHCPv6 option. You cannot do it without DHCP. Here is the RFC: https://tools.ietf.org/html/rfc3633


8

Every time a system starts to use a new IPv6 address (doesn't matter whether it is the link-local address, generated by SLAAC, provisioned using DHCPv6 or in some other way) it does Duplicate Address Detection, DAD, to check if the new address does not conflict with another device on the same link. There are usually settings on a system to disable DAD, but ...


7

DAD checks if the IPv6 address you try to use is already taken by another device. It works over the Neighbor Discovery Protocol, exactly over the Neighbor Advertisement Portion of it. The DAD of DHCPv6 is the same than the DAD of SLAAC. Inside DHCPv6 you use the DAD 2 times. First for your link-local address before you start DHCPv6 and than with the address ...


6

A Stateful address assignment involves someone keeping track of the State. Which is to say, some system exists that provides a log that certain IP addresses were assigned to certain MAC addresses. DHCP / DHCPv6 keeps truck of such information. A Stateless address assignment does not keep track of what has or hasn't been assigned. It simply determines what ...


6

RFC 4862 really describes routers within a single administrative control. RFC 7084 clarifies how customer routers should behave. This gives an ISP some freedom in how it supports IPv6 to its customers. To the PE router, the CE router is a host. From the perspective of a LAN (layer-2 domain, including the link from PE to CE), a router really is just another ...


6

Why does RFC 4862 say "Since host autoconfiguration uses information advertised by routers, routers will need to be configured by some other means." The people who wrote that document (and it's predecessor RFC 2462 ) almost certainly had a worldview that there were two types of devices. "hosts" that were numerous and a burden to manage and "routers" that ...


5

After experimenting with this, I have made a few discoveries that end up dictating which path to choose. Multiple subnet advertisements means multiple IPs in the same subnet If you have multiple routers advertising the same prefix, you don't end up with redundancy, you end up with multiple IP addresses in the same prefix/subnet. This is like assigning ...


5

DHCPv6 makes use of T1 and T2 timers. T1 timer is usually 50% of the preferred lifetime value. T2 is 80% of the preferred lifetime. When T1 timer expires, the DHCPv6 client sends a RENEW message. On receiving no response from the server, it waits until T2 expires and then sends a REBIND message.


4

OK, so I have revisited this issue several times, and now have working IPv6 with TWC via my SRX. I wish I could mark several answers and comments as correct as several of you gave me parts of the overall solution. Thank you all, for that. I've upvoted the answers that contributed to give as much as I could to contributors. As it turns out, the DOCSIS ...


4

If you're seeing duplicates with DHCPv4, it's very likely you'd see the same with DHCPv6, because the problem is with your DHCP server and/or configuration. Both systems work exactly the same, addresses generally aren't recycled until they have to be. (when a lease expires, the address becomes a "tombstone" -- expired but still in the database as ...


3

The link-address is the address of the DHCPv6 server on the LAN where the DHCPv6 request came in. It is mostly used with DHCPv6 relays. DHCPv6 messages usually have link-local source and destination addresses. When those are sent to a relay, the DHCPv6 server that receives the relayed message has no idea what link the original message came from. Therefore ...


3

Prefix delegation through a site can be performed via DHCP relay chaining; each router in the chain bootstraps the next. The PD should be originated internally to allow you to scope the subnets accordingly. My only concern is how to build resilience in to this. Also, my provider has only given a /56 which makes this method not very scalable with that amount ...


3

Stateful configuration Stateless configuration (also known as SLAAC-StateLess AutoConfiguration) The stateful version of DHCPv6 is pretty much the same as for IPv4. Our DHCPv6 server will assign IPv6 addresses to all DHCPv6 clients and it will keep track of the bindings. In short, the DHCPv6 servers knows exactly what IPv6 address has been assigned to what ...


3

First of all, in IPv6 there is no longer one single 'lease time', but now two values determine an address/prefix lifetime. This is used in both SLAAC and DHCPv6. The preferred lifetime, during which you can use an address as you like. The valid lifetime, during which you should no longer use the address for new connections (e.g. when creating a socket), but ...


3

Not related to your specific problem, but you'll need to permit ICMPv6 to come back to you (Echo Reply, Echo Request and Packet too big at least) because IPv6 doesn't support fragmentation and Packet Too Big messages is the only way you (your SRX, PC etc) will know to send smaller packet.


2

Lease time indicates the amount of time the IP will be leased to that particular client. Most of the time, DHCP client makes a renew attempt when the half duration of lease time passes, and will cut the waiting time to half after each unsuccessful attempt(goes like: waits 50% of lease time, then waits 25% of lease time). If it cannot make a renew, it will ...


2

Came across this, and not sure if you ever got this working, but I was just working on the same thing, trying to get TWC working with an SRX. After some debugging, I found this in the traces: Jun 17 20:50:41 [DEBUG][default:default][N/A][INET6][ge-0/0/0.0] dhcpv6_client_validate_msgs: Server does not have rapid commit. I had it working on a Cisco where I ...


2

Make sure that you do not have the dhcpd deamon running (set system services dhcp). When running dual stack you'll need to be running your internal dhcp through the jdhcpd deamon (system services dhcp-local-server). Its a bit odd, but the dhcpd deamon stomps on the jdhcpd deamon.


2

Theoretically, you can assign any number of IPv6 addresses to a single interface. Practically, each OS has a limit, but the limit is far more than two. Each IPv6 interface will normally have a link-local, and a global address assigned, and you can assign other global or ULA addresses, in the same or different networks via combinations of stateful and ...


2

If you take a look at RFC4862 (IPv6 Stateless Address Autoconfiguration) this behavior might become a little clearer: The autoconfiguration process specified in this document applies only to hosts and not routers. Since host autoconfiguration uses information advertised by routers, routers will need to be configured by some other means. So in other words:...


2

In IPv6 there are two ways of dynamic address assignment. One is SLAAC (StateLess Address Auto Configuration), the other is DHCPv6. DHCPv6 can be used to only assign additional informations (DNS resolvers, NTP, ...) or only addresses or both. In IPv6 the router tells the client which method to use via flags in a an mechanism called router advertisement (RA)...


1

You have something assigning ULA (Unique Local Addressing) addresses on your network. ULA addressing can be used within your network, but it cannot be used on the public Internet. ULA addresses are in the fc00::/7 range, but the 8th bit is to determine if the addresses are locally assigned. The fc00::/8 range is reserved, and the fd00::/8 range can be ...


1

The 2811 router is fairly old and End-of-Life since 2016, with the last software updates in 2014 (over four years ago). Your IOS version probably does not support this command. You always need to look at the IOS versions where the command was introduced: Cisco IOS IPv6 Command Reference - ipv6 dhcp relay destination Also, this does not seem like a CCNA-...


1

Whatever is doing hostname resolution is returning link-local IPv6 address(es) that aren't valid for the interface selected -- i.e. "any". Link-local addresses must specify the interface -- eg. fe80:...:1%eth0 Why you're getting a link-local address is unknown. Perhaps people familiar with Arch linux could provide further assistance. (Also, ip -6 [route|...


1

My instructor answered my question. Cisco routers will not insert an IPv6 default route into their routing table unless you do a "no ipv6 unicast-routing" command. I tested this in GNS3 and I can now ping R1's global address from R2. This is apparently the same situation with IPv4, but I haven't tested it yet.


Only top voted, non community-wiki answers of a minimum length are eligible