Differences

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--- doc:appunti:net:ipv6_on_ppp [2024/07/05 15:31] – [Troubleshooting IPv6 problems] niccolo
+++ doc:appunti:net:ipv6_on_ppp [2024/07/05 15:37] (current) – [Troubleshooting IPv6 problems] niccolo
@@ Line 582: / Line 582: @@
 <code>
-ping -6 2a01:4f8:1c17:7636::1
+# ping -6 2a01:4f8:1c17:7636::1
 </code>
@@ Line 588: / Line 588: @@
 <code>
-ip -6 address show dev enp0s7
+# ip -6 address show dev enp0s7
 </code>
@@ Line 603: / Line 603: @@
 In the example above the interface have two **global** scope addresses, one assigned via DHCPv6 and the other obtained via SLAAC. The first one has the **dadfailed** flag, which means that the **duplicate address detection** has detected a conflict in the network. This means that the IP address in question will not be used as the source address and it does not even respond to a self-ping.
-If you have only one global IP address which is **dadfailed**, you cannot reach remote hosts on IPv6. It may be a difficult situation to diagnose, because using the simple **ifconfig** command you see the assigned IPv6 address and default route is OK:
+If you have only one global IP address which is **dadfailed**, you cannot reach remote hosts on IPv6. It may be a difficult situation to diagnose, because using the simple **ifconfig** command you see the assigned IPv6 address and the **default route** is OK:
-<code>
-ip -6 route show
-</code>
 <code>
+# ip -6 route show
 a02:2420:503:1c03::2 dev enp0s7 proto kernel metric 256 pref medium
 a02:2420:503:1c03::/64 dev enp0s7 proto kernel metric 256 expires 86387sec pref medium
@@ Line 616: / Line 613: @@
 </code>
-**NOTICE**: The default router can be reached via its **link** scope address (as above) or via its **global** scope address, both can be used.
+**NOTICE**: The default router can be reached via its **link** scope address (as seen above) or via its **global** scope address: both can be used.
-If you sniff the ping request on the router, you can see the problem:
+If you sniff the ping request on the router, you can see the problem more clearly:
 <code>
+# tcpdump -i eth0 -n 'icmp6'
+...
 IP6 fe80::225:22ff:fedd:4598 > 2a01:4f8:1c17:7636::1: ICMP6, echo request,
     id 56698, seq 1, length 64
@@ Line 627: / Line 626: @@
 </code>
-the client uses its link scope address as source address, which causes the **beyond scope** error. You can confirm this problem on the client using the ''ip route get'' command:
+The client uses its link scope address as source address, which causes the **beyond scope** error. You can confirm this problem on the client using the ''ip route get'' command:
 <code>
-ip -6 route get 2a01:4f8:1c17:7636::1
+# ip -6 route get 2a01:4f8:1c17:7636::1
 a01:4f8:1c17:7636::1 from ::
     via 2a02:2420:503:1c03::1
@@ Line 642: / Line 641: @@
 <code>
-ip -6 route get 2a01:4f8:1c17:7636::1
+# ip -6 route get 2a01:4f8:1c17:7636::1
 a01:4f8:1c17:7636::1 from ::
     via fe80::d003:a6ff:fef2:6fe8
@@ Line 650: / Line 649: @@
 </code>
-In the first case the **src** address is the **link scope** one, not suitable for routing. In the second case it is the one received via SLAAC, which has a **global scope** and indeed it is working. Notice that the address of the router (shown as the **via** address) is not releveant, the //link scope// one does work.
+In the first case the **src** address is the **link scope** one, not suitable for routing. In the second case it is the one received via SLAAC, which has a **global scope** and indeed it is working. Notice that the address of the router (shown as the **via** address) is not releveant, even the //link scope// one does work.