JN0-106 Routing Fundamentals Practice Question
Which TWO statements about route preferences in Junos are correct?
⚠ Common exam trap
Watch out — candidates often confuse Junos default preference values with Cisco IOS administrative distance values, particularly for BGP (170 in Junos vs. 200 in Cisco) and static routes (5 in Junos vs. 1 in Cisco), leading them to select incorrect options based on Cisco knowledge.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Direct routes have a default preference of 0.
In Junos, direct (connected) routes have a default route preference of 0, which is the highest possible preference, ensuring they are always preferred over other route types for directly attached networks. Option C is correct because OSPF internal routes (both intra-area and inter-area) have a default preference of 10 in Junos, which is lower than most other dynamic routing protocols, making OSPF routes more preferred by default.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The preference of a route cannot be changed.
Why it's wrong here
In Junos, route preference is not fixed; it can be modified through routing policy by using the 'preference' statement to override the default value for matched routes. This mechanism allows network administrators to influence path selection, for example, making a BGP route preferred over an OSPF route. Therefore, the claim that preference cannot be changed is incorrect.
- ✓
Direct routes have a default preference of 0.
Why this is correct
Direct routes, representing directly connected networks via active interfaces, are automatically assigned a default preference of 0 in Junos. This exceptionally low preference value ensures they are always the most preferred route source, taking precedence over all other route types like static, OSPF, or BGP routes. This mechanism is fundamental to Junos's routing logic, satisfying the question's requirement for a correct statement about route preferences.
- ✓
OSPF internal routes have a default preference of 10.
Why this is correct
OSPF internal routes in Junos are assigned a default preference of 10, which indicates that they are less preferred than direct routes (0) and static routes (5) but more preferred than OSPF external routes (150). This low value ensures that internal OSPF routes are selected as the active route when competing with less-preferred protocols. This is a correct statement about Junos route preferences.
- ✗
Static routes have a default preference of 10.
Why it's wrong here
Static routes in Junos actually have a default preference of 5, making them more preferred than OSPF's 10 and BGP's 170, but less preferred than direct routes at 0. A preference of 10 is the default for OSPF internal routes, so attributing it to static routes is a common misconception. The default preference can be overridden with routing policy, but the out-of-box value for static is 5.
- ✗
BGP routes have a default preference of 200.
Why it's wrong here
BGP routes in Junos are assigned a default preference of 170, not 200, and this value is used for both internal and external BGP routes unless overridden by policy. A preference of 200 does not represent any standard Junos route type, so this statement is incorrect. Adjusting BGP's preference via routing policy is a common way to manipulate route selection.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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