Male JRT aggression toward male dachshund

We brought home a male JRT when he was 8 weeks old, and we introduced him to an older male dachshund. The dachshund was very irritable and snappy towards the puppy (and aggressive), and the puppy didn't back down. The puppy tried to play with the dachshund, yet the dachshund responded with growls and snapping and some biting. For a while, the JRT acted as if this were all play, but now the JRT is 8 months old, and he's intact (he'll be neutered soon), and he is very domineering toward the dachshund. The JRT actually pins him to the floor, drags him around by the ears, or mounts him. Physically, the dachshund is no match for the JRT, and the JRT overwhelms him. The dachshund has a kennel, and the JRT used to chase him into the kennle and then leave the dachshund alone once the dachshund was in this *sanctuary,* but lately the JRT goes in after him and even pulls him out. The JRT has not bitten the dachshund, nor has he truly been serious in his attacks, but I'm getting concerned that this is not play but a heightening level of aggresiveness. Also, the JRT now dislikes any and all dachshunds. If he sees one, he'll immediately dominate it, whereas he doesn't do this with other breeds. I thought a dachshund would be able to fend a JRT off, but this is absoluetly not the case. The JRT overpowers any dachshund he sees, and I need to be vigilant when a dachshund walks by or my JRT will chase it and try to dominate it. I didn't know dogs could learn to dislike breeds, so I guess I have 2 questions: 1) What do I do about the aggression towards the dachshund at home; 2) How do I train the JRT so that he's not aggressive with dachshunds in general? Overall, the JRT is a great tempered dog; he's never caused a fight (although he doesn't back down), never nips people, has a very sunny, playful disposition, and is eager to please and obeys commands, even the *down* command.