Routing

Question 1

VPC Routing

What does the VPC Router route traffic between?

Answer 1

Between subnets, external into VPC, from VPC to external

Question 2

VPC Routing

Why doesn’t the VPC Router handle routing traffic /within/ a subnet?

Answer 2

Because routing isn’t required! Layer 2 MAC is sufficient! Routing starts when you leave the local subnet!

Question 3

VPC Routing

Where in the VPC’s network space can you find the VPC Router?

Answer 3

Subnet + 1 (every subnet). It’s the “default gateway” from DHCP Option Set

Question 4

VPC Routing

High-level, what are the entries in Route Tables associated with?

Answer 4

Subnets: routing is inter-subnet

Question 5

VPC Routing

How does VPC handle disambiguation when a Subnet is associated with two VPC Route Tables?

Answer 5

Can’t: trick question – Subnets only associted with 0 or 1 Route Tables.

Question 6

VPC Routing

How does routing work in a Subnet without a Route Table?

Answer 6

Trick: can’t happen, if no custom RT, Subnet uses default RT

Question 7

VPC Routing

Why should you leave the main Route Table alone (system-supplied defaults)?

Answer 7

In case you disassociate a Subnet from a custom RT, don’t want unintended consequences.

Question 8

VPC Routing

Within a Route Table, how are routes disambiguated?

Answer 8

Highest priority wins: longest CIDR prefix, then static routes, then propagated routes

Question 9

VPC Routing

What routes are present in all newly-created route tables?

Answer 9

CIDR range as destination, with target set to “local”.

Question 10

VPC Routing

How do you change this default route?

Answer 10

Can’t.