Routing policies (simple, weighted, latency) in AWS - Step-by-Step Execution

Process Flow - Routing policies (simple, weighted, latency)

User DNS Request

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Check Routing Policy Type

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Simple

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User gets IP

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Connects

User DNS requests are routed based on the chosen policy: simple returns one IP, weighted distributes traffic by weights, latency returns the lowest latency IP.

Execution Sample

AWS

User requests DNS -> Check policy -> Return IP based on policy

Shows how DNS queries are answered differently by simple, weighted, and latency routing policies.

Process Table

Step	Routing Policy	Input Request	Decision Logic	Returned IP	Reason
1	Simple	Request for example.com	Return single IP	192.0.2.1	Simple policy returns fixed IP
2	Weighted	Request for example.com	Select IP based on weights (70% 192.0.2.1, 30% 192.0.2.2)	192.0.2.1	Weighted policy chooses IP with probability
3	Weighted	Request for example.com	Select IP based on weights	192.0.2.2	Weighted policy chooses IP with probability
4	Latency	Request for example.com	Measure latency to IPs, choose lowest	192.0.2.3	Latency policy returns IP with lowest latency
5	Latency	Request for example.com	Measure latency to IPs, choose lowest	192.0.2.4	Latency policy returns IP with lowest latency
6	-	-	-	-	End of routing decisions

💡 Routing ends after returning IP based on policy logic

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	Final
Returned IP	None	192.0.2.1	192.0.2.1	192.0.2.2	192.0.2.3	192.0.2.4	Varies per request

Key Moments - 3 Insights

Why does weighted routing sometimes return different IPs for the same domain?

Because weighted routing distributes traffic based on assigned weights, so different requests can get different IPs as shown in steps 2 and 3.

How does latency routing decide which IP to return?

Latency routing measures network delay to each IP and returns the one with the lowest latency, as seen in steps 4 and 5.

Does simple routing ever change the returned IP?

No, simple routing always returns the same single IP, demonstrated in step 1.

Visual Quiz - 3 Questions

Look at the execution table, what IP does simple routing return at step 1?

A 192.0.2.2

B 192.0.2.1

C 192.0.2.3

D 192.0.2.4

💡 Hint

Check the 'Returned IP' column at step 1 in the execution_table.

At which steps does weighted routing return different IPs?

A Steps 1 and 2

B Steps 4 and 5

C Steps 2 and 3

D Steps 3 and 4

💡 Hint

Look at the 'Routing Policy' and 'Returned IP' columns for steps 2 and 3.

If latency to 192.0.2.3 increases, which IP might latency routing return instead?

A 192.0.2.4

B 192.0.2.2

C 192.0.2.1

D 192.0.2.5

💡 Hint

Latency routing picks the IP with lowest latency; see steps 4 and 5 for examples.

Concept Snapshot

Routing policies control how DNS answers return IPs:
- Simple: returns one fixed IP
- Weighted: distributes traffic by weights
- Latency: returns IP with lowest network delay
Choose policy based on traffic needs and performance.

Full Transcript

Routing policies in AWS DNS decide how user requests get IP addresses. Simple routing always returns the same IP. Weighted routing splits traffic among multiple IPs based on assigned weights, so different requests may get different IPs. Latency routing measures network delay and returns the IP with the lowest latency to improve performance. This visual shows step-by-step how each policy picks the IP to return for DNS queries.

Practice

1. What does a simple routing policy do in AWS Route 53?

easy

A. Sends all traffic to a single resource

B. Splits traffic based on weights

C. Routes traffic based on lowest latency

D. Routes traffic randomly among resources

Solution

1. Step 1: Understand simple routing purpose

   Simple routing sends all user requests to one resource without splitting or conditions.

2. Step 2: Compare with other routing types

   Weighted routing splits traffic, latency routing chooses fastest server, so they differ from simple routing.

3. Final Answer:

   Sends all traffic to a single resource -> Option A

4. Quick Check:

   Simple routing = single destination [OK]

Hint: Simple routing means one destination for all traffic [OK]

Common Mistakes:

• Confusing simple routing with weighted routing
• Thinking simple routing balances traffic
• Assuming simple routing uses latency

2. Which of the following is the correct way to configure a weighted routing policy in AWS Route 53?

easy

A. Assign weights to each record to split traffic

B. Set a single IP address for all traffic

C. Use latency measurements to route traffic

D. Randomly assign traffic without weights

Solution

1. Step 1: Identify weighted routing configuration

   Weighted routing requires assigning numeric weights to DNS records to control traffic distribution.

2. Step 2: Eliminate incorrect options

   Single IP is simple routing, latency routing uses latency, random without weights is invalid.

3. Final Answer:

   Assign weights to each record to split traffic -> Option A

4. Quick Check:

   Weighted routing = assign weights [OK]

Hint: Weighted routing needs numeric weights per record [OK]

Common Mistakes:

• Confusing weighted with simple routing
• Using latency instead of weights
• Not assigning any weight values

3. Given two servers in different regions with latency routing enabled, which server will Route 53 direct a user to?

medium

A. The server with the highest weight

B. The server with the lowest latency from the user

C. The server with the most traffic

D. The server randomly chosen

Solution

1. Step 1: Understand latency routing behavior

   Latency routing sends users to the server with the lowest network delay from their location.

2. Step 2: Exclude other options

   Weight is for weighted routing, traffic volume is not a factor, random choice is not latency routing.

3. Final Answer:

   The server with the lowest latency from the user -> Option B

4. Quick Check:

   Latency routing = fastest server [OK]

Hint: Latency routing picks fastest server by user location [OK]

Common Mistakes:

• Mixing weighted and latency routing concepts
• Assuming traffic volume affects routing
• Thinking routing is random

4. You configured weighted routing but all traffic still goes to one server. What is the most likely cause?

medium

A. DNS records have different names

B. Latency routing is enabled instead of weighted

C. Simple routing policy is selected by mistake

D. Weights are set to zero for other servers

Solution

1. Step 1: Check weight values in weighted routing

   If weights for other servers are zero, all traffic goes to the server with non-zero weight.

2. Step 2: Rule out other causes

   Latency routing or simple routing would behave differently; different record names do not affect routing weights.

3. Final Answer:

   Weights are set to zero for other servers -> Option D

4. Quick Check:

   Zero weights = no traffic [OK]

Hint: Check weights are not zero for all servers [OK]

Common Mistakes:

• Confusing routing policy type
• Ignoring zero weights effect
• Assuming DNS names affect weighted routing

5. You want to route 70% of traffic to a primary server and 30% to a backup server, but also ensure users connect to the lowest latency server within those groups. Which routing policy setup should you use?

hard

A. Use latency routing only with weights assigned

B. Use simple routing with latency routing

C. Use weighted routing with latency routing inside each weight group

D. Use weighted routing only without latency

Solution

1. Step 1: Understand combined routing needs

   You want to split traffic by weight, then route users to lowest latency server within each group.

2. Step 2: Identify correct routing policy combination

   Weighted routing controls traffic percentage, latency routing directs users to fastest server inside each weighted group.

3. Step 3: Eliminate incorrect options

   Simple routing cannot split traffic; latency routing alone can't assign weights; weighted routing alone ignores latency.

4. Final Answer:

   Use weighted routing with latency routing inside each weight group -> Option C

5. Quick Check:

   Combine weighted + latency for split and speed [OK]

Hint: Combine weighted and latency routing for split and speed [OK]

Common Mistakes:

• Trying to use simple routing for traffic split
• Ignoring latency inside weighted groups
• Assuming latency routing can split traffic by weight