10 Juniper SRX Interview Questions and Answers

Juniper SRX is a robust and versatile firewall and security platform widely used in enterprise and service provider networks. Known for its high performance, scalability, and comprehensive security features, Juniper SRX devices are integral in protecting network infrastructures and ensuring secure data transmission. With capabilities ranging from intrusion prevention to advanced threat intelligence, mastering Juniper SRX is essential for network security professionals.

This article offers a curated selection of interview questions designed to test and enhance your knowledge of Juniper SRX. By working through these questions, you will gain a deeper understanding of the platform’s functionalities and be better prepared to demonstrate your expertise in a professional setting.

Juniper SRX Interview Questions and Answers

1. Describe the process of configuring a basic security policy on an SRX device.

Configuring a basic security policy on a Juniper SRX device involves defining security zones, assigning interfaces to these zones, creating address books for source and destination addresses, and setting the security policy to specify actions like permit or deny.

Example:

set security zones security-zone trust interfaces ge-0/0/1.0
set security zones security-zone untrust interfaces ge-0/0/2.0

set security address-book global address trust-subnet 192.168.1.0/24
set security address-book global address untrust-subnet 0.0.0.0/0

set security policies from-zone trust to-zone untrust policy allow-http match source-address trust-subnet
set security policies from-zone trust to-zone untrust policy allow-http match destination-address untrust-subnet
set security policies from-zone trust to-zone untrust policy allow-http match application junos-http
set security policies from-zone trust to-zone untrust policy allow-http then permit

2. Explain how to configure NAT (Network Address Translation) on an SRX device.

Network Address Translation (NAT) modifies network address information in packet headers, allowing multiple devices on a local network to share a single public IP address. To configure NAT on an SRX device, define NAT rules and apply them to interfaces. Here, we focus on source NAT.

Example configuration:

set security nat source pool POOL-1 address 203.0.113.1/32
set security nat source rule-set RULE-SET-1 from zone trust
set security nat source rule-set RULE-SET-1 to zone untrust
set security nat source rule-set RULE-SET-1 rule RULE-1 match source-address 192.168.1.0/24
set security nat source rule-set RULE-SET-1 rule RULE-1 then source-nat pool POOL-1

In this example:
– A source NAT pool named POOL-1 is created with the public IP address 203.0.113.1.
– A rule set named RULE-SET-1 is defined to apply NAT rules from the trust zone to the untrust zone.
– A rule named RULE-1 is created to match traffic from the source address range 192.168.1.0/24.
– The matched traffic is then translated using the source NAT pool POOL-1.

3. How do you configure and verify IPsec VPNs on an SRX device?

Configuring and verifying IPsec VPNs on an SRX device involves defining the IKE proposal, policy, and gateway, as well as the IPsec proposal, policy, and VPN. Security policies must be configured to permit traffic through the VPN, and the configuration and status of the VPN should be verified.

Example:

set security ike proposal ike-proposal authentication-method pre-shared-keys
set security ike proposal ike-proposal dh-group group2
set security ike proposal ike-proposal authentication-algorithm sha-256
set security ike proposal ike-proposal encryption-algorithm aes-256-cbc
set security ike proposal ike-proposal lifetime-seconds 3600

set security ike policy ike-policy mode main
set security ike policy ike-policy proposals ike-proposal
set security ike policy ike-policy pre-shared-key ascii-text "your_pre_shared_key"

set security ike gateway ike-gateway ike-policy ike-policy
set security ike gateway ike-gateway address 203.0.113.1
set security ike gateway ike-gateway external-interface ge-0/0/0.0

set security ipsec proposal ipsec-proposal protocol esp
set security ipsec proposal ipsec-proposal authentication-algorithm hmac-sha-256-128
set security ipsec proposal ipsec-proposal encryption-algorithm aes-256-cbc
set security ipsec proposal ipsec-proposal lifetime-seconds 3600

set security ipsec policy ipsec-policy proposals ipsec-proposal

set security ipsec vpn ipsec-vpn ike gateway ike-gateway
set security ipsec vpn ipsec-vpn ike ipsec-policy ipsec-policy
set security ipsec vpn ipsec-vpn bind-interface st0.0

set interfaces st0 unit 0 family inet address 10.0.0.1/30

set security zones security-zone trust interfaces st0.0
set security zones security-zone untrust interfaces ge-0/0/0.0

set security policies from-zone trust to-zone untrust policy vpn-policy match source-address any
set security policies from-zone trust to-zone untrust policy vpn-policy match destination-address any
set security policies from-zone trust to-zone untrust policy vpn-policy match application any
set security policies from-zone trust to-zone untrust policy vpn-policy then permit tunnel ipsec-vpn ipsec-vpn

To verify the IPsec VPN configuration and status, use the following commands:

show security ike security-associations
show security ipsec security-associations

4. Explain the concept of zones in SRX and how they are used in security policies.

Zones in Juniper SRX are logical entities used to group interfaces and define security boundaries. Security policies control traffic between these zones based on source and destination addresses and traffic type. By default, traffic within the same zone is allowed, but traffic between different zones is denied unless explicitly permitted.

Example:

set security zones security-zone trust interfaces ge-0/0/1.0
set security zones security-zone untrust interfaces ge-0/0/2.0

set security policies from-zone trust to-zone untrust policy allow-http match source-address any destination-address any application junos-http
set security policies from-zone trust to-zone untrust policy allow-http then permit

In this example, two zones are created: trust and untrust. Interfaces ge-0/0/1.0 and ge-0/0/2.0 are assigned to these zones, respectively. A security policy is then defined to allow HTTP traffic from the trust zone to the untrust zone.

5. How would you troubleshoot a failed BGP session on an SRX device?

To troubleshoot a failed BGP session on an SRX device, follow these steps:

1. Verify the BGP configuration, including neighbor settings, AS numbers, and authentication.
2. Confirm IP connectivity between BGP peers using ping and traceroute.
3. Use show bgp summary to check the BGP session status.
4. Review system logs for BGP-related errors with show log messages.
5. Ensure no firewall filters block BGP traffic, particularly TCP port 179.
6. Verify route policies to ensure they are not filtering out BGP routes.

Example commands:

show configuration protocols bgp
ping <peer-ip>
traceroute <peer-ip>
show bgp summary
show log messages | match bgp
show configuration firewall

6. Explain how to configure and manage virtual routers on an SRX device.

To configure and manage virtual routers on an SRX device, use routing instances. Virtual routers allow multiple logical routers within a single SRX device, useful for segmenting network traffic.

– Create a Virtual Router:

set routing-instances <instance-name> instance-type virtual-router

– Assign Interfaces:

set routing-instances <instance-name> interface <interface-name>

– Configure Routing Protocols:

set routing-instances <instance-name> protocols ospf area 0.0.0.0 interface <interface-name>

– Route Import and Export:

set routing-instances <instance-name> routing-options static route <destination> next-hop <next-hop>

– Monitoring:

show route table <instance-name>.inet.0

7. Describe the process of configuring Security Intelligence (SecIntel) on an SRX device.

Security Intelligence (SecIntel) on an SRX device provides threat intelligence to identify and block malicious traffic. It uses threat feeds to dynamically update firewall policies.

To configure SecIntel:

– Enable the feature.
– Configure threat feeds.
– Apply SecIntel policies to security zones or interfaces.

Example:

set security intelligence enable
set security intelligence threat-feed feed-name <feed-name> url <feed-url>
set security intelligence policy <policy-name> match source-address any destination-address any
set security intelligence policy <policy-name> then deny
set security zones security-zone <zone-name> security-intelligence-policy <policy-name>

8. Describe the steps to configure a chassis cluster for high availability on SRX devices.

Configuring a chassis cluster for high availability on SRX devices involves enabling the cluster, assigning cluster and node IDs, setting up control and fabric links, defining redundant interfaces, and creating redundancy groups.

Example CLI commands:

set chassis cluster cluster-id 1 node 0 reboot
set chassis cluster cluster-id 1 node 1 reboot

set interfaces fab0 fabric-options member-interfaces ge-0/0/1
set interfaces fab1 fabric-options member-interfaces ge-5/0/1

set interfaces reth0 redundant-ether-options redundancy-group 1
set interfaces reth0 unit 0 family inet address 192.168.1.1/24

set security zones security-zone trust interfaces reth0.0

set chassis cluster redundancy-group 1 node 0 priority 100
set chassis cluster redundancy-group 1 node 1 priority 1

9. Explain how to configure Advanced Threat Prevention (ATP) on an SRX device.

To configure Advanced Threat Prevention (ATP) on an SRX device, ensure you have the necessary licenses, define security policies for traffic inspection, create ATP profiles, apply these profiles to security policies, and configure logging for threat monitoring.

Example configuration snippet:

set security utm feature-profile anti-virus juniper-express
set security utm feature-profile anti-virus juniper-express default
set security utm feature-profile anti-virus juniper-express http
set security utm feature-profile anti-virus juniper-express ftp
set security utm feature-profile anti-virus juniper-express imap
set security utm feature-profile anti-virus juniper-express pop3
set security utm feature-profile anti-virus juniper-express smtp

set security policies from-zone trust to-zone untrust policy allow-http match source-address any
set security policies from-zone trust to-zone untrust policy allow-http match destination-address any
set security policies from-zone trust to-zone untrust policy allow-http match application junos-http
set security policies from-zone trust to-zone untrust policy allow-http then permit application-services utm-policy av-policy

10. Explain how to implement Role-Based Access Control (RBAC) on an SRX device.

Role-Based Access Control (RBAC) regulates access to network resources based on user roles. Implementing RBAC on an SRX device involves defining user roles, assigning permissions, and associating users with roles.

Example:

set system login class read-only permissions view
set system login class read-only deny-commands configure
set system login class admin permissions all

set system login user alice class read-only
set system login user bob class admin

In this example, two roles are defined: read-only and admin. The read-only role has limited permissions and is denied access to configuration commands, while the admin role has full permissions. Users alice and bob are then associated with the read-only and admin roles, respectively.