![](/static/network-academy/shrimpco/banner.png) # Lab 7 - PAT & Dynamic Routing > Shrimp Co. requires enterprise-grade infrastructure for reliable operations. Implement full redundancy with dual distribution switches, OSPF dynamic routing, and PAT for scalable internet access. ==- Lab Topology ![](https://raw.githubusercontent.com/network-chadmin/containerlab/refs/heads/main/network-academy/shrimp-co/diagrams/07_pat-dynamic-routing.png)

Tip: Individual topology files are available in the diagrams folder on my Github

=== ### :icon-tasklist: Configuration Tasks #### Layer 2 Configuration Ensure access ports, trunks, VLAN databases, and port-channels are configured to span Layer 2 domain across all access and distribution switches. - **VLAN 10** – Sales - **VLAN 20** – Engineering - **VLAN 99** – IT #### 1. Configure Gateway SVIs (VRRP) On both distribution switches (`sea-mdf-dsw1` and `sea-mdf-dsw2`), configure SVIs with the following addresses and enable VRRP: - **VLAN 10:** `10.1.10.1` (VRRP VIP) - **VLAN 20:** `10.1.20.1` (VRRP VIP) - **VLAN 99:** `10.1.99.1` (VRRP VIP) Assign actual IPs (.2 and .3) to the switches. Configure VRRP priority so that `dsw1` is preferred for VLANs 10 & 99, and `dsw2` is preferred for VLAN 20. #### 2. Enable OSPF on Routers and Distribution Switches - Use OSPF process ID **1** across all routing devices. - Use **exact network statements** to advertise networks into OSPF (do not summarize). - Advertise: - All point-to-point links between routers and distribution switches - Loopback interfaces - VLAN interfaces (distribution switches only) - Configure all interfaces in **area 0**. - Use the command `passive-interface default` under OSPF configuration mode. Form adjacencies only on /30 transit networks and between VLAN 99 SVIs. !!!warning "Multi-Vendor Simulation" These labs simulate a common real-world scenario: a multi-vendor environment. While OSPF operates the same under the hood, vendor syntax will differ. Reference the documentation for both platforms to configure it correctly. !!! #### 3. Configure PAT on Routers - On both `sea-mdf-r1` and `sea-mdf-r2`, configure PAT (port address translation / overload). - Use **standard access-list 1** to specify exact source subnets for NAT/PAT. #### 4. OSPF Default Route Injection - Configure a static default route with a next-hop of the Volt Communications provider edge router. - Inject this default route into your OSPF process so that it is learned by both distribution switches. --- ### :icon-check-circle: Success Criteria +++ Primary Goals - **VRRP** - VLAN 10 & 99 are *Master*, VLAN 20 is *Backup* on `sea-mdf-dsw1`. - **OSPF Convergence** - Each distribution switch has **three** full adjacencies; each router has **two**. - **SeaMart Server Reachability** - Every host can ping SeaMart's IP address (`123.123.123.123`). - **OSPF Default Route Injection** - Default route on the distribution switches is learned dynamically via OSPF. +++ Stretch Goals - **VRRP Efficiency & Security** - Configure VRRP timers for faster failover and enable MD5 authentication. - **OSPF Packet Capture** - Use `tcpdump` on a distribution switch interface where you expect to see OSPF Hellos. - **Name Resolution** - Enable Linux hosts to resolve and curl seamart.com with either method you've learned so far. +++ ### :icon-terminal: Verification Commands +++ Router Commands (IOS) ```bash # NAT translations show ip nat translations # OSPF show ip ospf neighbor show ip ospf interface [Ethernet0/1] # Default route in routing table show ip route ``` +++ Distribution Switch Commands (EOS) ```bash # Verify VRRP show vrrp [brief] # OSPF show ip ospf neighbor show ip ospf interface [Ethernet5] show ip ospf summary ``` +++ Host Commands (Linux) ```bash # Validate HTTP reachability curl http://123.123.123.123 # Show routed path to a destination traceroute 123.123.123.123 # Test DNS resolution nslookup seamart.com ``` +++ ### :icon-question: Questions to Explore * When designing a network, why might you choose VRRP instead of HSRP? * From your OSPF Hello packet capture, what information can you extract about neighbors and timers? * Why is your OSPF learned default route on the distribution swiches labeled differently than the others? * What advantages does dynamic routing like OSPF offer over static routing? ==- :books: Documentation - [EOS 4.34.1F - OSPF Configuration](https://www.arista.com/en/um-eos/eos-ip-routing) - [IP Routing: OSPF Configuration Guide (Cisco IOS XE)](https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe-16/iro-xe-16-book/iro-cfg.html) - [EOS 4.34.1F - NAT Configuration](https://www.arista.com/en/um-eos/eos-nat) - [EOS 4.34.1F - VRRP and VARP](https://www.arista.com/en/um-eos/eos-vrrp-and-varp) ===