Sorry I am new to ipv6 summarization and is trying to figure out the summary address for these 3 loopbacks
1: 2001:db8:0::1/128
2: 2001:db8:0::2/128
3: 2001:db8:0::3/128
Reference CCNP ENCORE book page 234
Answer is : 2001:db8:0:0::/65 network
My confusion is why 65 instead of 126 because it is only the last 2 bits changing or different?
Another example from page 279
3 loopbacks to summarization again
1: 2001:db8::1/128
2: 2001:db8::2/128
3: 2001:db8::3/128
Answer is 2001::db8:0:0::/62
Can someone send a link with Good explanation and some practice questions to master ipv6 summarization?
Hi there,
Are you sure you have copied those example subnets, because in both although syntactically different the expanded values are the same, ie:
2001:db8:0::1 == 2001:db8::1
Reverse engineering from the answers you gave the component prefixes that fit would be:
2001:db8:0:0:1::/128 2001:db8:0:0:2::/128 2001:db8:0:0:3::/128 summarised by: 2001:db8:0:0::/65
...and...
2001:db8:0:1::/128 2001:db8:0:2::/128 2001:db8:0:3::/128 summarised by: 2001:db8:0:0::/62
Either you have copied the questions down incorrectly or you should submit some more errata to the already long list here:
https://www.ciscopress.com/store/ccnp-and-ccie-enterprise-core-encor-350-401-official-9780135262030
Play around with subnets here (https://subnettingpractice.com/ipv6_subnetting.html) using the summary prefixes given as the answer, and note how the component prefixes I specify above fit within them, when the format is exactly the same.
cheers,
Seb.